I have helped a number of sprouts new to my FC do dungeons (and totally not because of first time bonus/second chance points, no siree!).
The reality is that even with he occasional dungeon to break it up a new player still has hundreds of quests they have to go through before they can get into the social aspects of the game and almost all that questing is something they will have to solo. In fact a lot of the time actually trying to help them with it is counter productive since they will lose exp for having a higher level player with them.
The long and the short of this is the amount of MSQ that a new player has to get through to get into the social endgame activities everyone else is doing it too much. Even when people enjoy it its a massive grind. Its like overeating on a delicious meal. The food can taste great but after a while you have eaten so much you really don't want to eat anymore at the moment. Its at that point, with 100s of quests to go, that I see most sprouts that leave, leave.
I think what a lot of existing players don't understand is that consuming the MSQ in one sitting is different to what most have experience. Even if you started in HW, imagine if you had to do all that but also had to do all the HW patches and all of Stormblood. All of that from the start of ARR in one go. Most of us experienced players have gotten to experience the story questing in broken up components spaced out with breaks between the chunks.
More over this problem will only get worse. In 4.0 a new player will have to level through 3 expansions and two full patch cycles before they get to current content. That will take people months. That's months of wading through story before you can group up with people to go do maps or run roulettes or raid.
Considering that the Jump potion would level you to the max lvl of the last expansion then doing that wouldn't really matter cause if you used it today you would be starting at lvl 50 with ilvl 110 gear.
The jump potion doesn't let you skip all levelling, only the levelling through the past expansions. Likely the Jump potion would come with a gear set about that level since it is likely going to be the required entry level gear to survive in Stormblood zones.