It’s admittedly not a fully formed thought, and you bring up good points (plus the Bucks won a couple years ago playing drop coverage), but playing drop coverage tends to lead to lots of 3s which teams are always seeking out these days.
Small sample size, and don’t know an efficient way to look at this over a larger sample, but in the Sixers playoff series this year, the Celtics made 25 more 3s overall, 28 more in their wins, and 32 more in the games Embiid played. That seems almost impossible to overcome (and yet the Sixers almost did).
It’s possible that teams that are better at it tend to have better perimeter defenders that can fight over screens and discourage the 3 and force the ballhandler to drive into the drop coverage as well as into more favorable areas of the floor (towards the wing instead of the top of the key), a second big that can help rim protect (Tatum/TL, Giannis, Aaron Gordon), multiple good-great off-ball defenders, ability to play non-drop with frequency. These are mostly/all areas Philly has lacked recently (although Ben Simmons helped with a lot of the above).
Some of that is roster construction, but that is sort of my original point. Embiid requires a very specific skill set around him at both ends of the floor to be successful in the playoffs when every weakness is relentlessly attacked.