Retrace what you're saying here:
Only ONE team can win in the playoffs; the other 15 teams have to lose. And since the game is
run by guards/wings, it stands to reason that all of them, bar one, will lose.
Joel's impact is limited because he can't run the offense; his impact is limited to when the ball-handlers give him the ball, so when he's not getting the ball he's having little-to-no impact on that end. Especially since he doesn't stretch the floor without the ball either. The more times touching the rock = the more you can influence the offense. Steph's the next evolution of this, but that's a conversation for another day.
It's why bigs like AD, Boogie, LMA and Embiid haven't lead their respective teams to top seedings nor had notable success in the postseason. There's only one big who runs contrary to that rule -
Jokic.
I'll let you work out why.
And it's not like the big men we have in today's league aren't
great players in their own respect, it's just they're playing in a climate which isn't conducive to them leading a winning-team. You put Embiid back in the 80s/90s, where post-play was the staple of offenses, and the three-ball wasn't in rotation like it is now, and he'd be leading his team on deep playoff runs. He'd be revered as a far greater player than he is now. He's just simply a casualty of the era he's playing in.