If people at startups weren't slightly naive, they wouldn't attempt an endeavour that has such a low success rate :)

This happens all the time.

Basically build vs buy. The problem is on the 'buy' portion of looking at things the company failed. So they took who they had on hand and built something. It took a fresh perspective to say 'hey have you tried this' and looks like they did not want to hear it. I would say the right choice was made to move on.

This is wildly common. At that point they were committed to the wrong path at 'above my pay grade levels'. Once you get that buy in you better do it that way. Most companies will not pivot unless the champion for whatever is going on is removed in some way.

At 'my paygrade' I can prototype tech but I better make a good case why I need everyone else to do it too. If I dont I will be summerly ignored at best, at worst 'the guy with the lets rewrite the system hahahaha' guy. I might even be right about it. But the probelm is a jr level guy is not going to have the political cover to make it happen. Even if they are right.

But if you can get 'the higher ups' to buy in. Then it is quite dramatic how much better somethings putting that sort of tech in. Then other times it can be a total disaster. So you have to pick your hill to die on.