I recently tried out Ironbar because waybar just really annoys me and I was impressed with Ironbars config which was essentially "yeah...use whatever the hell you want."

linux already has a standard, which it inherited from unix: plain text.

structured text is good but there is always some edgecase that needs to be worked around. plain text is universal.

there are alno verification functionality in basically every core utility.

I see and feel what OP does. As a newbee to Linux (I guess, a lot in EU want to switch to Linux nowadays) it is really hard to learn which config file will how be used for which tool. As with the nature of Linux, that it has grown organically since years, plain text has been around since decades.

Are there any tools around to create config files easier? It is like programming without much knowledge and I guess a lot of "normal" users stick with Windows or Mac because of this.

In abstract, I guess maybe there would be some benefit, but I've been using Linux for decades, and it really hasn't been an issue for me. I've definitely had times where configuring stuff is confusing, but it's not a function of the basic input format not being JSON or XML or TOML or YAML or whatever. I think that the only time that I recall tabs being obnoxious was not with config files, but with Makefiles (they do, in fact, require tabs).

The majority of software is packaged with an "example" config file, often with comments in place. Traditionally, software will also ship with a section 5 man page for its config files. So, for example:

$ man 5 fstab

Will describe the format for /etc/fstab.

EDIT: I think that the biggest hassle I recall was in configuring a sendmail mail server, quite some years back. The issue there wasn't the basic format, but the fact that due to organic growth, even basic configurations were enormous (just to get the sort of common configuration that most users wanted) and required quite a bit of reading through the option documentation. It was common to use a frontend to generate the config files, and a number of subsequent mail servers aimed at having their default, no-configuration-options state being closer to what people wanted, dramatically reducing the number of options that had to be specified.

Of course a challenge in the Linux ecosystem would be coordinating this change to happen widely and at once (which is important from a UX perspective). Since each of the aforementioned files belongs to a different project, and each project has its own maintainers that would need persuading (or rather inviting to the table to agree on a single format).

Try nix, its esentially JSON with functions

Spoken like a true ignorant noob. JSON is hot fucking garbage. TOML is ok. Plaintext is GOAT.