1961 the AL went from 154 to 162 games.
1962 the NL went to 162.
Divisional play started in 1969, and added a single round of playoffs between the top finishers in each division.
I'm not sure when the "season is too long" arguments started, but they've been around for a while. Average game times have gone from about 2:30 to just over 3 hrs in the same period of time we've had 162 games. I think the longer games tend to drag out, and people lose interest, and that makes the whole season seem way too long. I try to get to a couple games a year, and most nights I'll either have the car radio on or the TV on in the background and listen in. Baseball is a long season, but it's just a part of the way I spend my summers (and spring, and fall)
https://www.baseball-reference.com/leagues/MLB/misc.shtml
The stats on that page claim average attendance per game last year was 28,000, not much different for the last 20-30 years. In KC, they tried moving game times around so more kids could get to the games - they started an hour earlier until the end of the school year when they went back to their normal starting time.
https://www.baseball-reference.com/leagues/MLB/2019-misc.shtml
Last year the Miami Marlins averaged 10,000 per game. My local team, the Royals, averaged 18,000.
And those hot August day games when it's 104 and there is crappy pitching and a lot of pitching changes, and the bats are quiet so it's a 1-0 game that has absolutely no action and your team is already 16 games out, yeah, those are no fun. I've sat through 1-0 games that are at both extremes of the fun:not-fun scale.