I've done a bit of thinking since it got revealed that Minkah Fitzpatrick would be the Team Builder 99 for this release. I think that Crystals have actually done more bad things for theme teams than anything good this year. My reasoning is:
A) Players that are also old Crystals can basically never be used on certain theme teams
B) They are unbelievably expensive due to being mostly locked behind bundles worth hundreds of dollars or just being basically unobtainable in packs
C) Their boosts are far, far too strong
Luckily, I think there are solutions to all of these problems. Starting with the issue of old Crystals making some cards unusable on theme teams.
For example, if you run a Philideplhia Eagles theme team, you effectively had to use HB Vick nearly the entire year since Saquon is a +1 speed Crystal, that there were no alternatives to until Foyesade and AJ dropped. Even if 94 Saquon isn't really elite anymore, he almost was never even an option because when he was, he wasn't worth sacrificing +1 speed to most of your team for. Similar things happened with Patrick Surtain and Fred Warner, and are likely going to happen when Micah Parsons, Leonard Williams and Trey McBride get new cards, among some of the others. I think this is solvable by either making the Crystals have less obscene boosts so that they aren't basically essential to all theme teams.
Of course EA probably won't change a thing, infact this issue will probably get worse and worse until it seriously harms the game, but that's just my wish. I think just nerfing the boosts they give, or alternatively, making it similar to how most program chems work could be completely fine. Just for example, If regular crystals gave, let's say +1 component and the LTDs gave +3 components to a, say 30 component chemisty that gave around +1 to most offensive or defensive stats, and +1 or 2 speed, that would be managable, and also probably stop cards like Saquon from being 2 million coins 4 months after release.
I think that's a lot better of a system then the way it is now, where some crystals just don't even give good boosts, and then some of them sit at 5M+ to get all three just for +1 speed. Or remove the boosts part entirely and just make them special 32 team chem cards. Those would still make EA a ton of money regardless. Anyways, rant over.