I went for a year (mid-March 2020 to March 2021) without being on a train or bus at all. When I went back it was tentative, a few stops at a time, double masked. In the before times I used to travel at rush hours some and coped with it. My most vivid memory of crowding was the time I was smashed against someone holding a toddler and realized that the damp feeling on my arm was the urine-absorbing gel bursting out of the kid's diaper onto me. Went home, took a shower, washed my clothes...
Now I can't stand being in a crowded space at all, and have decided against the Green Line, which always seems too stuffed for my taste. I've added a good bit of walking to avoid it. T buses seem more full than the Red line trains, but have better masking compliance sometimes and are less air-tight. Supposedly the federal public transportation mask mandate will end on September 13th, and the T is planning to go with that, unless somebody decides that Delta is going to get us all if we stop masking and extends the policy.