At first, I didn't know how to feel about this, I felt cheated that new players will be able to simply skip all of the content that *I* had to go through fair and square. It already made me half angry when very incompetent players are clearing ex primals and coils like it's nothing because lolol unsync.
But in the end, these things are necessary, unsync for new players to experience old content, because learning old content the hard way might be impossible with everyone running the current stuff.
And same goes for these jump potions, it might feel like there's not that much story content to go through, but it piles up and for someone casually playing few hours each week, it will take months to get up to the most recent content, that's further elevated with the next expansion. I recently see it with my friend, I bought him the game, it's his second month playing and he's on level 46 ATM, still 2.x and 3.x to do before he'll be able to join in to the recent stuff with me. Now he doesn't mind at all, he enjoys the experience but for most people this will be a deal breaker (got 2 other friends in game, one quit after level 30 the other after 40)
Jump potions will help people get started and it will give them a reason to stay around instead of leaving out of frustration because "there's so much to do before I can play with my friend that are already in end-game". So yeah, I came to the conclusion that this can only help the game, for those willing to pay up to catch up and can't see themselves going through the whole thing... You'll either have people play or have them leave somewhere because they can't be bothered to do it all.