Some of the stuff I told them:
THE GOOD
De-coupling Race from Culture
Overall it's the right thing to do and I like most of the design moves that support it, including MOST of the race changes. Exceptions below.
De-coupling Ability Scores from Race
I liked in in Tasha's and I still like it here.
Backgrounds
Pushing "make your own" as the primary thing to do is good. The suggested packages make sense to me.
Characters of mixed race/heritage
This is a better way to handle things and while I will miss both the mechanical half-elf and half-orc nostalgically, this is the right way to go.
THE BAD
Inspiration
I don't think "free inspiration on a long rest" will entice people to play humans as strongly as Variant Human did. I don't like Inspiration on Nat 20s because I think Inspiration should come from non-mechanical stuff like good roleplaying, storyline goals, or just being a good player/nice person at the table - not from dice rolls.
d20 Tests
I hate auto-fails on Nat 1s and auto-success on Nat 20s for Skill checks.
The "if it's impossible, don't let them roll" argument doesn't always apply, mainly because there are some situations in which a thing is impossible, but you as DM don't want to tip your hand that it's impossible. For example, players encounter what they think is a person, but it's a actually a programmed illusion or construct performing a pre-determined routine. They try to "Persuade" it to do something. If I refuse a roll, I tip my hand that something is "off" with the creature. If I allow a roll and they get a Nat 20, what am I supposed to do? I don't want to be compelled to give a success on a nat 20 in that situation.
Finally, auto-fail on a nat 1 hurts players a lot more than auto-success on a crit helps them. If a thing is doable, a 20 was gonna succeed anyway. But if the player has invested a lot in that particular skill, a 1 might not have failed - now it definitely will.
I'm fine with it on Saving Throws.
Critmas is Canceled
Removing crits from spell attacks sneak attacks, and smites removes fun. Nobody wants this. The argument that "most players don't even know you can crit on these" is, in my experience, nonsense. And I have legitimately played 5E with ~1,000 people at this point.
The motivation for removing crits from enemies seems to be "it's not fun when your level 1 character gets splattered by one lucky shot from a goblin." The game probably is too swingy/deadly at level 1, but I think just giving level 1 character 2 hit dice so they can survive one mistake or 1 bad hit is a better solution than taking away enemy crits.
Dwarf, Your Tool Proficiency is From God
Bizarre choice and contrary to their overall direction. Also, not setting agnostic.
Dragonborn
The Fizban's direction was better than this.
THE MIXED
Arcane/Divine/Primal spells
I like the mechanical diversity this lends in certain cases. But I don't like the game telling me exactly where my character's magic comes from - I would rather be left to flavor that myself. Also, I have been playing with some people for years who still haven't really wrapped their heads around the CURRENT eight schools of magic and what they mean; this is just adding one more thing they'll never really understand.
Feats for Everybody
Level-gating some feats helps mitigate the power creep, but it's still power creep. I do LIKE most of the Feats here, and I do recognize that a LOT of people want universal Feats at level 1, so this change is at least a legitimate response to player demand. Character creation is already the most confusing part of the game for new players, and adding one more thing for them to deal with I'm not crazy about. I do think though that this will help some folks express their character concept better. I'm torn on this one. If they go nuts with Feat Chains I will 100% hate it.
Tieflings
I like the Chthonic and Abyssal tieflings, but I miss the diverse tiefling options offered by Mordenkainen's Tome of Foes.