Heroku was one of the first to have that seamless UX, only after which others like Fly or Render or Railway came to copy it. I wager people were primarily attracted to that user experience and only minimally cared that it was fully hosted versus not, because there was also AWS at that time.
Having used Heroku at multiple startups during the 2012–2015 years, this is not correct.
With heroku you could `git push heroku master` and it would do everything else from there. The UX was nice, but that was not the reason people chose it. It was so easy compared to running on EC2 instances with salt or whatever. For simple projects, it was incredible.
That's literally the UX I'm talking about and that's what other companies copied too. To be clear, I'm not (just) talking about how heroku.com looks and works, I'm talking about the entire user experience including git push to deploy, so I believe you are agreeing with me here. That is why I said VPS with Dokploy or Coolify and so on have the same UX, both in the command line with git push deploys supported as well as (now, at least) a vastly superior website user experience, akin to Vercel.
Dokku is better. And neither is what Heroku's bread and butter customer needs.
But alas, my interest in painstaking explaining why self-hosting is fundamentally incompatible with a product who's value prop was "nothing to install" is waning.
You and I simply have different opinions on what Heroku's value proposition was, because, again, AWS was also right there and also was "nothing to install." Therefore Heroku was used primarily for its dead simple UX, something which is replicated even in a self-hosted environment, because, again, the value prop was never about PaaS or self-hosting, it was always about the user experience.
Realistically, self-hosting the PaaS defeats the purpose of a PaaS for the crowd Heroku was attracting.