I'm a PHP Dev—and I fucking hate WordPress
Or, if you're going to implement a templating language, use Handlebars or Twig instead of trying to roll an inconsistent half-assed version using html comments and JSON strings.
Disclaimer: I normally try to avoid talking about work-stuff but there is just some shit that is seriously bugging me right now about WordPress.
WordPress' push towards full-site editing and block themes has been frustrating, to say the least. Lack of documentation being a huge part of that frustration, and changing features between major versions is another.
Then there's the little things like modifying a parameter in that embedded JSON string but the site editor isn't smart enough to look at that parameter and "go hey, I need these classes" and add them. Instead, it just throws an unexpected content error at you.
That issue right there throws the claim "oh you can still code these templates in an IDE or text editor like normal" out the window. Especially when the code inside the html comment is touchy about spacing, or the templates themselves don't have an opening/closing tag structure that makes sense.
The editor not being smart enough to recognize a parameter and add the needed classes was today's frustration. It's not a hard feature to implement—I know WP devs who have developed blocks that do it automatically. There is no reason in the world why WordPress can't do the same.
Finally, Gutenberg needs a serious UX audit. Settings are in the block tool-bar when they should also be included in the side bar is frustrating, to say the least. It's namely layout settings—like the Cover block, for instance. Vertical alignment settings for the content inside the block are actually on the block's tool-bar, but if you're looking for them in the side bar, they're not there. Either put them in both spots, or eliminate one of them if you can't be bothered to be consistent.