I think the Mage changes are a good idea BUT they should've been accompanied by other ones as well
The overall idea is good; Lower the impact of wave clearing by having mages choose between fighting their opponent, clearing waves and actually manage their mana. Mana costs are insignificant nowadays and this is in theory a great change.
BUT It should not be the only change.
By nerfing mages, a lot of other things that are currently out of whack are only going to be made worse.
Namely two important things that also push stagnation more than mage wave clear does.
Those being: A) Jungle impact just being way too high
And
B) ADC's spiking too hard/being too strong early.
Both of these issues should've been resolved at the same time to actually make the game more interesting and redistributing position impact.
Tougher clears, more deawbacks from failed ganks and overall more risk involved in ganking a lane would actually make laners interact more instead of having to fear for a jungler to gank and just screw everything up.
Likewise, ADC's power curves should've been addressed as well as having their actual role fleshed out more. Like reducing their overall mana-less wave clear by changing shiv as well as making them not spike at TWO bloody items.
You should fix EVERYTHING at once and not make just one class suffer while others are allowed to get away with their BS for far too long.