I keep answering this and then deleting my response. This time I will just stick to the question, rather than addressing any answer. Follow the rules me!
I lived in Boston or within subway distance for 45 years, and took the subway (T) for all of that time from 5-7 days per week to a couple of times per month...depended what the era of my life was.. As far as I'm concerned, there is no better way to travel around Boston than by the T. Keep in mind when fresh out of college I was assigned the territory of Boston in my first job and was scared to death to learn how to drive there. Shortly, I knew all the shortcuts in all the area towns. Still, the best way for commuting or enjoying Boston was(is) by the T. OK, hop forward. I moved away a couple of years ago. Since then they have had issues with tracks and trains, which always happens with transportation, but a little more than usual this year. Nonetheless, it is running and carrying people the same as always in most spots, if not all, but a little slower in some areas (red line I hear). I always had a book with me and so never was bothered if there was a delay...,more time to read! I have found it safe, but when riding the T around 10:00-10:30 on my line, no reading, heads up, and I'd prefer a pick up if getting off at a non-populated spot. But this is me, a woman, anywhere.
Also, I have not been out and about in Boston for a couple of years, that I can think of...the Covid thing. I understand that the financial district has not recovered its population yet due to telecommuting, but all the other areas, where you are most likely to be, have returned to pre-covid busy-ness according to a recent article that I read...and by the amount of tourists in the area.
As a T rider, in a T community, I learned there were some people who refused to ride the T as they somehow felt it was beneath them. They would speak ill of it for no reason as they never rode it, and to me, LOL, who they knew rode the T all the time. So be sure to listen to those who actually ride the T. And again, I've been out of it, other than the commuter train from up here in the north. Boston is a lovely city and I doubt it has changed so horribly in 2 years...and I'm sure my friends would have mentioned it if it had.
Also, my husband drove through Boston twice last week on the Southeast Expressway and reported that there was less traffic than usual. He sailed right through and back again in record time; so much for the traffic always being terrible.
PS. You posted while I was writing. From Quincy, T by all means. Just be sure to get on the Braintree line, but I'm sure your relatives will tell you that.