I have an ok chest now [will post updated photos once gyms open, so I can get a proper pump], but it took me 15 years of training before I had a chest that got to the standard I wanted.
Basically, I think genetics play a big role in everything. Look at Arnold's chest - you can see he has amazing chest genetics, and I think he could have had a big chest doing push-ups.
I'd be willing to bet Arnold could have had an above average chest with 25-50% of the work he put in.
I'm not refuting the importance of flat bench - I'm just saying genetics seem to trump everything.
Your gyms are still closed? Ours (in Florida) got reopened in June of last year but with restrictions. Kids' club is still locked down. They JUST reopened pools and saunas last week.
At first, you had to make a reservation on line and could only stay for an hour. The 24-Hour Fitness app had to have your picture, so you could check into the club without the fingerprint thing.
They closed for 30 minutes to clean. Well, at the particular club where I'd train, they'd only close for 10 minutes. Everyone had to wait outside until they were done. For example, if you're reserved to train at 5pm, the club closed at 6pm for cleaning with the next opening at 6:30.
But, if you waited outside and they got done early (i.e. 6:10 or 6:15), you could go back inside to train until the 6:30 people showed up; then you had to leave. If some showed up but there was space still available, the 5pm folks could go back inside.
Two months later, they dropped the reservation thing. It's first come, first serve, until the gym is at capacity. But, hours are still reduced, as the club closes at 9:00pm and reopens at 5:00am.
As for your pecs, perhaps going wide-grip will make a difference. I'd recommend the Smith Machine, as you can get your hands as wide as you need, without worrying about pinching them on the uprights. But, I train alone. If you have a partner, doing the barbell will work better.