I think the change away from Apexes in 2.10 has more to do with new dinos being added than the actual nerfs.
Part of it is that people seem to overreact to ANY nerf without actually following it’s implications. Honestly Ludia could probably say “Reduced Hadros Luxes HP to 5100” (it’s current value), and some people would STILL freak out just because of the word “reduced”.
In 2.9 there were only two Apexes in the meta, and we all know who they were. They got nerfs in 2.10, but I don’t think those on their own should have done much. As others have said it was a bit of a 1-2 punch of nerfs and powerful new dinos, but I personally put FAR more blame on the new dinos, namely because the Apex changes are very disproportionately small compared to how people perceive them now.
Magnus was strong because of it’s powerful swap in attack. It still has that attack, but now it does 200 less damage. The other changes don’t really amount to much, only being slightly slower with slightly less armor, and getting crits 10% less often. Still, this is definitely a nerf. But it’s not such a massive nerf that Magnus lost the core of what it is or what it could do. By itself, it should NOT have been enough to drop Magnus from your team or make it not worth raiding for.
Hadros is similar. Granted, it’s nerfs were a bit more significant, but it should still be good. It’s counter still inflicts vulnerable, and it still has a rampage on turn 1. It did lose it’s other rampage, but at least now it can slow. And it lost 150 attack. I won’t pretend it’s just as good as before, but like Magnus these changes alone should not have been enough to make Hadros irrelevant.
So why are players dropping these dinos? I don’t think it’s because they’re particularly bad, but because other dinos are good. You only get 8 slots on your team, so people are going to use the 8 best dinos. Magnus was used as a swap in, and people typically seem to run only 1 or 2 swap in attackers on their team. In 2.10, Magnus got some very strong competition from Phorurex for this slot, and even being slightly worse allows other swappers like Monolorhino to catch up. I think this is generally good though, since players have more of a choice depending on their team and the meta. Magnus still has an edge in group acceleration, giving it a priority strike on turn 1. Since Monolorhino has the same swap in attack, Magnus will almost always outdamage Monolorhino on turn 1 in the same situations.
Hadros is a bit different. In 2.9 it was so broken that there was pretty much nowhere to go but down. The thing is, 2.9 Hadros also to some extent masked just how strong some other dinos like Skoona and Testa were. While the changes to Hadros made it reasonably strong, Skoona and Testa are pretty much just as strong as before, so they’re not unreasonably strong, and outcompeting Hadros for a teams “strong resilient” slot. And you also have other strong uniques like Scorpius, Phorurex, and Indominus competing for this slot as well. Yes this means uniques are beating an Apex for a slot on your team, but it’s more because the uniques are too strong than from the Apex being too weak relative to the general balance curve.
It’s like on a scale from 1-10 (with 10 being the strongest), you ideally want Apexes at an 8 or 9 and Uniques at a 7 or 8. 2.9 Hadros was at a 10, stronger than it should have been. Stuff like Testa and Skoona were also overtuned, being at around a 9, but these were overshadowed by just how strong Hadros was. 2.10 rightfully nerfed Hadros, bringing it to around an 8.5 or 8. Maybe slightly on the weak end, but still around as strong as an Apex should be relatively to most uniques. And notice that I said MOST uniques: it’s really just a few of the most recently released or buffed uniques that are the problem here. Most of the older unique dinos like Indoraptor, Smilonemys, Trykosaurus, etc. are still weaker than or at most around as strong as Hadros is now (so it’s not like ALL uniqes are better than the Apexes). But since Skoona and Testa are still basically as strong as they were before, they’re still at a 9, only now that makes them preferable to Hadros. But the problem isn’t necessarily that Hadros was nerfed too much, but that these dinos were previously buffed too much. A big part of me thinks that this is intentional, since Ludia makes more money by rotating the top tiers out, making you pay more money to invest in the new ones every month. Ideally, they would expand the size of the group of high tier viable dinos instead of just rotating out the OP dino of the month, but they won’t do that because it isn’t as profitable.