I like building stuff that people use, not writing papers about about how to build things that people will almost certainly never use.
So, in this end what did you do? Are you able to build product you care about now?
I've never regretted leaving academia for a single moment - that's not to say I don't have fond memories and I learned a lot there but ultimately I have always liked building stuff and ultimately that's only worth it if people get value from what you build. I knew a lot of great people in academia - but I was conscious that there was very much a game to be played (as is the case everywhere) and the game from what I could see wasn't one that interested me.
Are you sure you are not harsh on yourself? :) Maybe it was a good paper. If you are so worried, you can always ask the conference reviewers for comments; maybe they thought it was excellent.
> useless crap
You get enough "useless crap" down as knowledge and, who knows, one day you get to flying cars or the proof of Goldbach's conjecture.
NB It probably didn't help that I spent 6 years working on symbolic AI at the start of the 90's at it was becoming increasingly apparent to me (correctly as it turned out) that this fundamental approach didn't really work no matter how fascinating it was.
It probably depends on the field, also on the supervisor, and how much clout or willpower the student employs to force through their own vision. I made it very clear during my PhD that I was in principle paying a significant sum to be a PhD student (comparing my PhD salary to what I could go and earn in industry), so my tolerance for constraints was low.
Suffice to say, I dropped out of college and chased a quick buck on IT. At least on my university, it as expected that you'll get to academia, and of my friends, those who didn't went to other career path, are still waiting for a place in academia.