as the ecosystem around it swirled, the web platform itself remained remarkably stable

There’s a cost to using dependencies. New versions are released, APIs change, and it takes time and effort to make sure your own code remains compatible with them. And the cost accumulates over time. It would be one thing if I planned to continually work on this code; it’s usually simple enough to migrate from one version of a depenency to the next. But I’m not planning to ever really touch this code again unless I absolutely need to. And if I do ever need to touch this code, I really don’t want to go through multiple years’ worth of updates all at once.

I’ve been using heroku for years and while some might complain that it has stagnated and mostly stayed the same since the salesforce acquistion, I think that’s been an asset.