The problem is definitely exacerbated by human behavior. There are almost always multiple turnstiles, but I've seen groups of people managing to block all of them simultaneously, figuring out how to use them...

The last time I was in NYC was 10+ years ago, but from what I recall, operating the turnstiles correctly required some experience: you need to know that they require manual operation (not obvious to first-time users), and then you also have to operate them at the correct speed (going too fast doesn’t let you through).

Systems with fare gates (i.e. most systems worldwide) don’t have these problems, because it’s obvious when you can pass through.

Then factor in lots of tourists/visitors (who aren’t used to this system) + aforementioned small stations.

That’s true for Metrocards and paper single ride tickets, but no longer an issue for OMNY.

Most delays with OMNY seem to be due to the fact that people need to unlock their phone or pick a card because they don’t have express transit enabled.

MetroCard was definitely a confounding factor too, but isn’t it still the case that you have to manually push the turnstile within a certain time frame?

(idk, maybe I was just a clueless tourist who didn’t know how it worked :P)

To your latter point, perhaps the MTA should work together with Apple and Google to improve the experience.