I hope this is an April Fools.
I really do. Are you really going to punish everyone, because you have appearently never played any game ever? If you think speed stats are too advantageous for flyers (even if there have been nerfs before), try a soft cap approach using diminishing returns first, if simply reducing speed-gain-per-level doesn't do, but hard capping at base speed? That doesn't even work with certain aspects of the game anymore. Most prominent example being to get your first wyvern eggs. Do you expect people to shoot up the whole scar, so your now super slow ptera can fetch the egg without combusting? Either that or someone of the tribe has to sacrifice their tame, as there is no way to outspeed them on any flyer but wyverns anymore.
Dinos in ARK and the way they interact with one another are mostly all about the math. Now that there are certain things in place, some dinos are (supposedly) meant to beat others in certain fields and circumstances, you have to make sure that changes to your game don't knock over these structures and since that is mostly about math, all that requires is reading values from tables, assuring that one is still bigger/smaller/tied with another.
And if you are not capable to even to do that, whoever was responsible of balacing here, I really begin to doubt your ability to do so.
So please, let this be an April Fools joke.
Nevermind the "there is no way to outspeed them on any flyer but wyverns anymore". Wyverns don't recieve their imprint bonus on speed anymore.
Yes, they have been nerfed... hard. Basically no flyers can level up movement speed, nor is imprinting giving any bonus to it. Also basically all their stamina pools went to hell, (e.g. my 1k stamina, lightning wyvern went down to 350 | 1400 stamina quetz went to 400-somethingish).