Its very obvious you have no idea what you're saying and clearly do not play Ninja in end game content or you would not be saying "bonus gapclosers".

Ninja being forced to use these for damage will put you into a position where you use it and die or you don't use it at all, lose it and lose dps.

Them being higher potency than normal GCDs means we need to use them to maximize our dps but mechanics that force max melee or require strict movement will stop us from using them and in turn stop us from using all of our burst.

In savage fights you do not want to gap close when you don't need to because they will often lead to death and there are often times where you will have to delay a gap closer. But Raiju cannot be delayed because its a combo skill from everything in our burst phase.

Raiju is nothing like freecure and you will not get more melee uptime from using raiju vs not using it because you should never be using raiton away from boss since they're used during your trick attack which requires melee range.

You very obviously think that you can just use raiju whenever you feel like it but you will not be clearing savage content when it has dps checks and you are not doing enough damage because you don't use raiton inside trick and can't use raiju because of mechanics aligning with burst phase.

They're not bonus gap closers because we never needed more gap closers to begin with, they're literally the biggest problem ninja has ever had.

You say "Why would you not use them?" Because they can and will cause you to die to mechanics.
There is so many reasons that could cause you to be unable to use them. E12S ramuh, shiva junction, titan junction, lions, every single mechanic in part 2 of E12S and that is just 1 fight. Each of your burst phases line up with a mechanic and you are forced to use them, you will not be able to do that anymore in Endwalker because using 4 or 6 raiju will not be possible during mechanics. You have to stay at MAXIMUM melee and gap closers bring you to MINIMUM melee which will kill you.

If you have never done endgame content before then don't speak of it like that because in normal content it literally doesn't matter what you do. You could literally never use raiju in normal content and it wouldn't matter whatsoever or you could use it every time and kill yourself 4 times a dungeon and it once again wouldn't matter other than making the clear a bit slower. Savage and Ultimate content you cannot do this. You cannot be killing yourself with your own skills and you cannot ignore raiju because ninja is being designed around using it in order to do damage. This means we are forced to use it as much as we possibly can and yet mechanics will stop us from using it.

Its poorly designed and it completely hinders ninja which used to be the melee class with the most free movement. Now its more limited than dragoon which is literally known as the floor tank BECAUSE of its BONUS GAPCLOSERS as you call them.