I think reading some of Lenin's earlier works such as "What Is To Be Done" should shed some light on this dilemma you're having. There are times when as a communist party it is necessary and justifiable to work within bourgeois parliaments, and times when it is not. When it starts to look like the Netherlands is getting closer to some kind of revolutionary situation it will make sense to abandon parliamentarism and begin work primarily in the more actively revolutionary sphere. Until then i think it makes sense to continue building class consciousness and militant labor organizations. However during this time ideological struggle within the party should be placed at the forefront of priorities, as unless the party itself becomes sufficiently revolutionary and militant in its theoretical outlook they will be unprepared to seize the moment to mobilize the masses when the opportunity comes. Instead if the level of Marxist-Leninist ideological education is insufficient and if the party line is overly reformist or trade unionist then they will either freeze and dither when the critical time comes, or worse they will side with the social democrats in repressing the most revolutionary section of the working class.

In short, your task is to ensure that your party grows through vigorous internal ideological struggle to become disciplined, organized and ideologically firm like the Bolsheviks, rather than end up like the Social Revolutionaries (Right SRs) or the Mensheviks. You must combat opportunism and liberalism. And most importantly you must get your comrades to read, read, read (and discuss with each other what they have read to deepen their understanding).

If a large marxist-leninist party does not exist, this may be the next best option given your cirumstances. You are also in the imperial core, so I think it would be very difficult to find a party that does not have at least some large issues in this regard.. If we do not have the means to have our own organization yet, it would seem somewhat reductive to try to create one, given how much time and energy that requires.

I tend to think of what Lenin said regarding reactionary trade unions. They need to be worked with as they are the main proletarian organizations. Trying to create your own "pure" union often serves the risk of just removing potential connections you could have made otherwise.

It really depends on the social conditions what path regarding these kinds of less ideologically coherent parties should be taken I think.

Currently grappling with this question myself, germany has 2-3 small ML parties, but there is one that is revisionist and doesn't support AES, but they have a bigger reach, higher budget and more (and more diverse) members

Since apathy and alienation are at an all-time high around here, I really don't know what to do

How long are you in this party? If in your experience you find that it's possible to alter some policies of the party, then it's definitely worth it struggling from the inside and fight for a more revolutionary line, even if it's not a "ML" party. I expect however, that sooner or later you'll find something in the party that cannot be changed because of limitations of the organization.

My view on being part of a dsa chapter full of actual socialists is that the people who have comfy professional jobs are not going to form the vanguard but they can still be useful if they have the right politics. We can do good work together in an accelerationist sense- ei making conditions less precarious and connecting organizing around labor, tenants, and municipal issues to a wider context of capitalism.

I can't do that with a ML party that struggles to have a book club.

Speaking as someone who has been part of highly ineffective ML parties and orgs in the past and became frustrated/burnt out with them, go where you are most effective in your area, ML or not. There are non-ML parties that do effective work and you can still spread class consciousness within them.

The growth of the revolution will not be linear. This is especially true when the largest formations that currently exist are heavily revisionist. It could be worth joining to learn the basic skills of a communist: how to organize, how to accept criticism, how to engage in ideological struggle. The only way to develop ideological and practically is to actually engage in struggle and not merely fence sit; "to read too many books is harmful." Joining mindfully and validating your frustration with revisionism is going to teach you a lot more than web browsing.

Lenin was not a member of a purely vanguard Marxist party either; the RSDLP contained genuinely vanguardist elements, but also thoroughly reformist ones that agitated for better labor conditions but downplayed and even abandoned their struggle against the repressive Tsarist state (i.e. "Legal Marxism"). Organizations such as DSA in the States and Die Linke in Germany are similarly "Legal Socialist" or "Legal Social-Democratic" parties; unlike pure reformist parties (SPD, British Labour) they openly criticize capitalism, but are afraid to openly challenge the liberal constitutional order for (admittedly valid) fears of being criminalized. But there are elements that are worth engaging with, just as Lenin did. There is no shame in splitting to protect the revolutionary faction from revisionists/liberals, but it's also not ideal.

I would suggest to engage in the party's associated organizations (youth orgs, student orgs). Look for what interests you, whether it is community/labor organizing, direct action, education, mutual aid, electoral campaigns, or even just showing up at a variety of the above and volunteering/baking cookies or something. If the party's organizations have an open political culture, there are bound to be activists you have affinity for. Develop your politics with those comrades, participate in readings/campaigns with your circle, and maybe evolve into a revolutionary faction. Only by demonstrating that the revolutionaries of the party are more capable of leading the proletariat than reformists can Marxist-Leninists in a left party gain hegemony over the broader social-democratic movement.

You could become a founding member of socialism with Belgian characteristics

Hey there! Someone who lives in a country with sixteen different communist parties here. My advice is to simply join the party you see has more chances to achieve the goals you have in mind for society (those being in your case a ML state, I suppose). Neither a large socdem party with zero interest in revolutionary politics nor a minuscule hardline communist party with zero influence will do, so it is up to your judgement to find the goldilocks party in that spectrum.

If you, for example, were in a vanguard party. Would this party be worth collaborating with or would they obstruct any and all attempts towards socialist takeover?

Are you happy with the direction taken and achievements the party has made in these last 5 years? Do you think their current plans are realistic, and are you happy with their scope? I think being pragmatic is the best course of action. Organizations that have their act together and have room for more radical ideas are hard to come by.

Unless you're willing to build a party from the ground up, build up a organizational framework that is able to fend off modern threats, and spend a decade maturing the organization as well as have the people to follow you along: I wouldn't bother splintering off.

Better than arguing with libs online.

But promoting class consciousness is a good thing. It’s something that’s desperately needed. From your brief description, it’s doing the organize agitate educate thing.