Most of the characters in MKX had at least 2 viable Variations, which allowed more flexibility on how to play a character. Most of the characters in MK11 were punching bags without a specific loadout, or at least had two slots accounted for. Several characters basically couldn’t combo without specific abilities equipped and/or their Armor Breaking move had to be equipped.
The emphasis on Custom Variations during the pre-launch marketing left a sour taste in many players’ mouths because Custom Variations were banned from Kombat League and tournaments until damn near the final update. That only exacerbated the point of many characters feeling half-baked until the game was basically finalized.
EDIT: Custom Variations still suck in Kasual. Lots of people cheat and used banned abilities since the game is no longer relevant in the competitive sector.
For the custom variation piece, dont forget: they dropped it out of nowhere with basically no fanfare in the Ultimate update and then MADE NO NOTABLE ATTEMPTS AT BALANCING IT GOING FORWARD.
I'm still so miffed that MK11 could have been the ultimate matchup machine with characters having options, counter-options, niche combos, entirely different game plans, etc.; but instead, all we got was Kitana up fan dead on arrival, giga tornado Cetrion, and hurt feelings knee jerk reaction over nerfing Sheeva. That, and 2-4 moves at most per character being worth using alongside certain variation combos being the objectively best combos like Cetrion and Kabal.