I don't think you need ARR for Shadowbringers. You could literally skip straight to Shadowbringers and by the end it's pretty good. I played during ARR release then never again, boosted to Shadowbringers when it came out because I thought the game was the same as WoW (where only endgame/current content matters) and it was still good. This was before NG+ also, so I had no way to go back and redo the old xpac content. Sure, it has a lot of references outside of the expansion that will not land, but it's totally fine as a self contained story. You'll have a few 'who the fuck is that' moments, but I'd imagine almost everyone who played ARR on release said the same thing when the Thancred / Lahabrea reveal was done. Endwalker definitely relies heavily on Shadowbringers though.
Honest question, is this your first FF game? It's not like traditional Final Fantasy games have lots of branching narratives and different endings where you set off to make your own mark on the world. You're the Warrior of Light and are going to do Warrior of Light things. ARR has a lot of the 'new adventurer earning their place in the world' bullshit and I'd say is prob the closest to traditional style 'Western MMO' of all of the expansions. It was inspired by and made to compete alongside WoW, so you have a lot of filler horseshit to slow leveling, pointless side quests, etc. Modern FF14 is basically a long ass single player RPG where you can play multiplayer content with your character at the end. Complaining about ARR is like complaining about Vanilla wow mechanics being clunky. No shit.
So this isn't really true. 11 and 14 are mostly skipped by the "Final Fantasy" community since they are seeing as weird abominations and not 'real' Final Fantasy games. The producers are looking to change that and basically are extending the Trust system down to cover ALL story content from ARR to Endwalker. Essentially, you'll be able to run every single MSQ dungeon with a group of NPCs instead of other people. Hopefully, they also streamline out some of the boring 'mmo' parts of ARR (which they've already done once) and refactor it to be about as long to go through as the other expansions.