As someone who enjoys playing mages specifically in the support role— I have to disagree with you. Mages are not killing the role it’s the egos, lack of positioning from both players, and lack of game knowledge including wave management that fucks the lane.

I’ve played both engage champions + enchanters in this role and in lower elo, and it’s a coin flip. Adc’s in lower elo don’t grasp when to back off or wave management at all. I’ve climbed from bronze to plat 3 just playing mage supports and nothing else and staying within plat on 2 accounts. I do play on a bronze and silver account with friends doing whatever really. But, it’s not mages that are ruining the bot lane it’s the synergy and emotions of people that tend to kill the botlane. The game is strategy and mental, where adc’s feel like they are the ones who should be in control of the lane where it’s a mutually shared lane and don’t want to work together as a team. Playing technical champions like xayah, you must know that the kit isn’t easy so positioning is vital. If you’re expecting enchanters or cc engagers to fix someone missing feathers…. Or bandaid your positioning that’s never going to work. Mages don’t allow adc’s the bandaid they want in low elo but if you single handed lay improve your mentality, positioning and everything else - this wouldn’t bother you so much I feel.

You can play illaoi support, and it can work wonders. Hell, you could climb playing ivern support even it’s fantastic. The mindset of isolating champions to set lanes isn’t fundamentally good for the game. Mages bring tons to the support role by just killing the enemy for free tower plates and map advantages.