I don't buy the better coaches theory. Most teams I see now do the same thing - penetrate, pass & cut. Good picking has disappeared. If anything
I would say that coaching is the same if not worse. The 3 point line has destroyed the game.
I'm not sure the coaching is any better now. However, I would argue that because more coaching is allowed to take place outside of the competitive portion of the season, the games themselves are far more heavily coached than they were a generation or two ago. Some coaches monopolize the players' time to the point where the players can't even take a breath without the coach's instruction. As a result, the style of gameplay seems more deliberate as every move is analyzed by the coach before proceeding.
Also, I would agree that the 3 pt. line has definitely changed how the game is played and how it is coached.
I just looked through my alma mater's basketball files:
The current coach is in his 8th season. As of this moment, the team has averaged 52.7ppg under his tutelage. That includes 3 district championships. His most successful team (in terms of W-L) averaged 60.4ppg. His regional final team averaged 49.5ppg. and failed to score 40 on 5 occasions that season (yet still won 3 of those 5 games). The program is 24 games over .500 during his tenure. I worked the table for a game that produced a 31-28 win. I said "never again" after that one. The opponent had open midrange jumpers the entire evening and couldn't make them, so I can't attribute the score to a terrific defensive display by both teams. During his tenure, the team has won 7 games while failing to score 40 points or more. Prior to that, the last time they'd won a game while failing to score more than 40 points was 1964.
I go back to the late '70s/early '80s (i.e. no 3 pt. line) and find a coach who spent 6 years at the helm. His teams averaged 57.7ppg. The team made only 1 district final and compiled a 59-73 record in his 6 seasons. The team's best W-L season produced a 12-11 record and an average 60.8ppg. Their worst W-L season yielded a 7-14 record and a 53.7ppg scoring average.
I'll go back one more time to the '60s and find another coach who spent 7 seasons at the helm. He compiled a 62-69 record with no district final appearances. His teams averaged 57.2ppg. His best team finished 17-3 and averaged 68ppg. His worst team finished 2-17 and averaged 55.5ppg.
IMHO, another factor here is the disappearance of the multi-sport athlete. It seemed like every mid-sized school used to have at least or 2 guys on the team who could shoot the lights out or could impact the game with their raw athleticism. Fewer of those kids are playing because their prospects on the baseball diamond are too good, or they're going "all-in" with offseason football lifting in pursuit of a scholarship. In the boys HS basketball games I've attended in recent years, I've been amazed at how many of the teams lacked anyone who could shoot consistently well. It's possible that it's just easier for teams to sit back in a zone now and watch the opponent not be able to shoot them out of it.
With regard to the question posed in the thread title, I don't know about boys basketball, but I'd say for girls basketball, the answer is "yes" and then some. Some girls programs are simply dreadful, and many of the dreadful ones have little hope of improving quickly because any above average players in the lower levels often gravitate toward the better programs rather than stick around and try to elevate the struggling program that could desperately use the help. It also seems like the worst programs have constant turnover with their coaches.