The National League waited a couple of decades though. They could probably have done the DH rule 20 years ago. But they knew that the hard-core fans will revolt so they did not dare to go through with it.
Today? Now it's 2022. Millennial fans are not interested in the game itself. They show up for the atmosphere so they do not mind buying expensive tickets and rip off prices for concessions.
The hard-core fans can stop watching. Not a big deal. MLB will write them off as the cost of "progress".
I’ve noted that too, in attending games, that many fans, especially younger, don’t seem to know what’s going on.
Among my nice memories of attending games when I was younger, was talking baseball with fellow fans at the game. Nowadays, the people sitting next to you often can’t talk about the game because they don’t know baseball.
Nowadays, these people at the game are taking selfies and sometimes not even watching the game. I think some of these people look at going to the game as some social event, and aren’t really baseball fans.