Here's a different idea. Eliminate the 3 pointer IN THE FIRST HALF ONLY! Start counting them in the second half. This incentivizes the midrange but avoids moving lines, changing court dimensions, incorporating difficult rules like a cap, 4-pointers, 2.5 pointers, etc. Simple: the 3rd and 4th quarters would look exactly like current NBA games, but each game would also feature 24 minutes of something a little more similar to pre-Curry hoops, with a very significant exception: today's shooting skills would still make open looks from downtown "good shots" for SOME shooters, even without the extra point, thus maintaining some of the current spacing. Scoring would go down only marginally, back to something reasonable, and each game would feature different strategic battles in both halves. It's the simplest, least complicated solution. Midrange and post play would be re-emphasized, practiced more and therefore those skills would improve (ie, come back). AND we still get 24 minutes plus clutch time/OT with exact same current rules!

PS: an even less extreme, but equally simple, variation would be a first half with a 26-foot line and a second half with current line.

PS2: other variations are 3s allowed only in 2nd and 4th quarters, or 3s allowed only in last 6 minutes of each quarter.