You're kind of asking 2 questions with this. When I think of a platform's maturity, I'm thinking of the ecosystem for producing and publishing content. Tools, so to speak. In that regard, PT is fine. It has all the things you need to create your channel and begin publishing content as well as a good system for feedback. So as for maturity I would say yes it's mature enough for people to start using it.

On to your second question:

do you think PT is ready to bring visibility to new creators?

No unfortunately not even close. There are very few big PT instances and even those that exist feel like they're almost starved for content. There are a decent amount of creators on these instances but little to no viewers. It feels very similar to the earliest days of YT (think 2006-2008), but even smaller than YT was back then.

I do wish it'd catch on though