Magento 2
I got myself a new job couple of months ago (yayyyyy) and went from writing in Typescript and using Aurelia webpack to Magento 2.
Although my colleagues are absolutely amazing, Magento 2 itself really isn't. Yes-yes I know HOW DARE I SAY THAT but hear me out... Magento 2 is amazing in some aspects (like any other software or framework), but sorry...you can't solve every performance problem by just caching everything and hoping for the best. Magento 2's documentation is fragmented, it's like a Call of Duty match where every developer does something their own way and hopes for the best (it's a free-for-all), but let's get back to the documentation - there are things in the documentation that aren't even supported...THERE ARE THINGS IN THE DOCUMENTATION THAT ARE SAID TO BE SUPPORTED BUT AREN'T.
That itself should be a big red flag, how are developers supposed to know the best practices for implementing new functions or overriding Magento's default themes (oh don't even get me started on overriding Magento blank or Luma themes) if the documentation doesn't align with what's actually possible to do in Magento.
I don't like to rant about these kinds of things, truth is that most software products have issues that are really irritating, but Magento just has a lot of these, to be honest. Caching everything just to be "fast", having module developers like Amasty (if you have worked with Amasty modules then you know). One of the biggest problems that Magento has isn't even related to the documentation or the product itself, but more related to the community, specifically the lack of community. Nobody really knows how you are supposed to correctly implement new things, they are all just guessing and for newer stuff there really isn't anyone to ask about it. Documentation is lackluster and new developers don't have anyone to ask about these issues.
That said, Magento has a lot of positive features as well, but some of the negatives outweigh the positives.