Still hate the possession arrow, defence hustles, makes a great play only for offence to retain the ball.
Brought in to speed up the game, meanwhile how long do reviews take. Used to have some nuances in jump balls to either steal the tip or start a break. Seriously takes maybe 15 to 20 seconds maximum to set it up if refs and teams don't fluff about. Could even live with a delay of game penalty if players don't immediately get into position.
Most disliked rule along with intentional fouls at the end of games. Need a biomechanics degree now so you know how to make a correct play on the ball. Liked the old days when the coach would tell the refs you were going to foul and just had to touch them after they caught it. This is where the game slows down whilst umpires have to keep reviewing fouls when everyone in the building knows what the intention is. If it's a mugging, that's what the unsportsmanlike foul is for. You nearly have to devote some training time to show kids how to do it.
As for old rules, I think college is the only real league where they have one and ones. To those that don't know, when the team gets in the foul bonus, the first few times if you miss the first you don't get the second foul shot. I like the added pressure and players have to make their shots and can make comebacks easier. Most games are foul a thons in the last minute, make it a bit more interesting. Even if it's just the 6th and 7th team foul.