I think you have encountered some projects built by undisciplined teams. That is not a reflection on the framework, rather a reflection on the people improperly using it.
I've repeatedly seen the same things over a 15+ year timespan.
Also why would you be afraid of coupling to the framework? It's not like you're going to be able to change the framework after the project grows, anyway.
It may be that slow tests are just easy to complain about, and there isn't much business value in doing that. Totally fine. But, other things come to mind: weird cottage industry of gems that did dubious things to speed up tests (and were prone to breaking), the skepticism around interactors, the hegemony of active record (the pattern). None of those are bad things, but they reinforced the fact that the technical values of the Rails community do not work for me.