The game expects you and actively encourages you to run a circus. When I played mystic elves and focused strictly on the mystic tomes, pretty much all the units I've unlocked were the same unit. No kidding or exaggerating - 6 or 7 same mages standing with their hands stretched out and having an elemental attack mostly dealing electrocuting damage. The only difference was that like 2 of them were "support", meaning they had single attack, but some healing as well and the rest didn't. Out of the 3 or 4 not-sparkly-mage units unlocked there was exactly one unit that was high tier and semi-capable of melee, some foggy looking teleporting panther.
A lot of the choices are extremely superficial or simply fake. Culture traits are example of that. You pick something with a cool name and in practice it's just a minor bonus and you play just like anyone else. There seems to be exactly one strong exception from that rule - the one city stellaris fanatical purifiers perk that you need to unlock by grind. +1 medal to ranged units? Whoa, amazing, shame you forgot that unit leveling sucks same ass it did in PF and +1 medals means giving your ranged units +4hp or sth, dumbass.
The game also absolutely loves moving stuff around for no reason and no gain and pretending it's a new mechanic. A lot of enchantments work like that - you get a full set of ones, for example, that just give your culture thing to non-culture units. Not only is it boring and samey, but also something that AoW3 would simply and quickly handle by an empire upgrade that would also add something unique on top to make it at least slightly interesting. Like making non-class units devout would also boost their resistance.
I just don't feel their approach to "making your own race".
AoW3: You want frostlings? They have strong support units, so maybe pick sorcerer. You can focus on two least resisted elements and get a t3 support that is not afraid of melee, gets an aoe debuffing attack that can stun and freeze and greatly supports the attacks of the rest of your army. Very cool and satisfying. Or go warlord, strong support for the frost weapons makes them potent in close combat and most warlord class units get them. Then maybe pick explorer, since two warlord class units are irregular and you've got the best racial t1 irregular in the game. Maybe go water for frost elemental. Air to spread freezing terrain? And so on and so forth.
Planetfall: Synergies and interesting synergetic builds? Um, well, if you pick a secret tech with strong unit/mod/spell then it's strong and when it's strong it's synergy! But at least we still have some fun racial diversity for secret tech units, like amazon purifiers having bows, dvar deploying trenches and syndicate being indentured, which is very cool.
AoW4: You want frostlings? Uh, we don't do races anymore. But pick whatever you want, including literally fiery looking shit straight from hell and cast some frosty stuff on it - ta-da, frostlings! Flavor-less and low iq, sorry.
At this point it's pretty obvious that AoW3, or rather the support and development AoW3 received with expansions and patches, was just a fluke.
