The answer is fewer pitches in the game and the ball in play more. Radical rule changes are necessary to cut 100 pitches out of every game from 350 to 250 or less.
Here is a quick list of suggestions: 3 Ball walks. 2 Strike punch outs. No more than 2 foul balls at 1 strike. A base on balls gets treated like a ground rule double. Take 1 or 2 players off the field and out of the batting order. Pitch clock of 12 seconds for balls not in play. 18 if it is hit. Get it - set up and pitch it again. No screwing around.
Change the game so at bats are 6 pitches max. Penalty for walks is high forcing pitchers to throw strikes. Hitters have to put it in play. Open up the field to change the value of a fair ball. As long as the analytics prize the Home Run & walks at the expense of all else the game sucks.
It is 1970's football with teams using 40 running plays and 20 passes and 13-10 scores. The NFL changed the entire game and it is far more entertaining now than it was then.
With these changes most at bats will result in resolution in 3 or 4 pitches most of the time. In addition star players plate appearances would go up by 30 or 40%. You would see Mookie Betts or Aaron Judge get 200+ more plate appearances over 150 games rather than seeing the 8th and 9th hitter 6/8 times. You might also see the return of the complete game if starters can get a few <=10 pitch innings in a start if they are dealing.
The game has to cut 1/3 of the time and get back toward a 2 hour event rather than 3 to become watchable. It is unlikely I will watch an entire post season game in all of their gory 3 1/2 hour bore fest. That would keep me up past midnight off of an 8:30 start. Get the games going at 7:05 and done by 9:15 by having pitchers throw strike 1 and batters looking to put it in play and run the bases more aggressively.
What is the most exciting play in baseball? IMO it is a bases loaded ball in the gap. There are at least 18 people moving with a purpose on those plays. 8 Defenders (only the opposite side OF is not truly in play). 4 Offensive players, 2 offensive coaches and 4 umpires. It is a ballet of activity and just beautiful to watch.
A home run involves 1 player - the outfielder jogging back to watch it sail out with the occasional jumping attempt. Somewhere around 5,000 times - it stops being interesting.