In the 2010s it was so bad that I gave up on the subway and either walked, Ubered or took the bus everywhere.When the MTA bus is better than the subway, things in NY are grim -- it was like the 80s & early 90s again.
The reliability has improved a bit, but the subway crime is also way, way up. So yeah, still a hard pass.
In the mid 2010s i had a reverse commute from Manhattan to Brooklyn and there was a few months where 3 days a week my full commute would take 2hr+ (midtown to sunset park) because the train just sat multiple times not moving. Especially on the bridge where it could be up to an hour just stopped.
The absolute worst time that I ever remember though was maybe in '89 or '90. The Lex-53rd st E/F station had a ton of ongoing construction and on weekends it was being used as a transfer station only that summer. All the staircases were closed and you could only get in/out via train -- this idea seems insane to me but that's NYC sometimes and especially in that era.
Anyway, my family and I were on a train passing through that station one Saturday or Sunday morning on the way to Queens and they made us exit the train inside the station as it was going out of service. Apparently a pipe had burst (I think?) and no trains were in service. The AC in the station was not working and it was maybe 90+ degrees underground. Plus water was leaking from everywhere. And there were hundreds of us trapped on a crowded, wet, dirty platform for like 4-6 hours while no trains were running and there was no way to get out.
Aside: that Belt Parkway story is why people from NY who live/work in Manhattan try to never fly out of JFK. That's the real solution. So much easier to get to EWR/LGA.