Disintegrate change to spell attack

One of my players (A soc) asked if disintegrate could be changed back to a spell attack.  (In 3.x it was a range touch and in 5.x that would make it a spell attack not a save.)

I am think about letting it as there are not many high level spell attack spells.  I know him being a soc he will be able to get advantage with it.  Also legendary resitances will no longer save you from the spell.  Also as a attack the spell will be able to crit (10d6+40 ave 75 to 20d6+40 crit ave 110.)

Does anyone have any other reason not to change it to a spell attach vs Dex save?

There are several more feats/features that can affect an attack roll.  Negatives include disadvantage if casting within 5' of an enemy, opponents taking advantage of cover or melee combat with allies and others.  I do get the request, I'd rather have the dice than have the DM roll a save every single time.  I built a 3.5 Wizard around the Orb spells (all attack rolls) just to avoid opponent saves.

I’d recommend not changing it to a spell attack since the game design of 5e was not balanced with that in mind. On average, it’s a lot easier to hit with attack rolls than saving rolls due to a monster's ac being lower while a lot of monsters have high dexterity or proficiency in the saving throw.