Realistically, for full casters, there's no feat that will come even close to bumping your casting stat. No feat will give you the bonuses to your save DC, PLUS an extra spell to use. At 8th level, you're getting up to a 4th level spell known per day. Considering, by that point, you only know 2 (or can ready 2 if you're a cleric or druid), that's a HUGE bump in versatility. No feat will come even close to that.
OTOH, for fighting types, it's a lot less necessary. If you're an archer type, Sharpshooter+ your inherent +2 fighting style makes an extra +1/hit and damage pretty redundant. Even if you're not taking the -5, the fact that you almost never have the -2 from cover means that you've essentially got that +2 all the time. Going from a +8 (3 for proficiency, 2 for fighting style and 3 for stat) to +9 is essentially gilding the lily. It's not all that necessary at 4th level, and your proficiency bumps will generally keep up with the Joneses after that.
Even a melee type fighter isn't really all that put out by not taking the stat bump. A 16 Str will generally keep you pretty competitive. Particularly in a campaign featuring magic weapons and the like. Jacking up a melee attack isn't exactly difficult - gaining Advantage, Bless spells, bonuses from this or that. Unlike a save DC which is pretty much static no matter what.