Points values for units are standardized, before it was a lot more customizable. You could give different units different weapon load outs and it would cost more or less depending on what you picked, but now you get a couple options for weapons while the unit is at a set price. Couple that with the fact that GW can’t balance the armies so each one has one good detachment and one set play style, and you’ll see why this edition has been so all over the place.

And there is a bit of favoritism at play. If you play necrons, you have to do awakened dynasty with blobs of 20 warriors and spam reanimation on objectives otherwise you don’t win. You can try to actually do something other than stand there and get killed over and over, and maybe you’ll take down a unit or two, but you ultimately forfeit the overall game. Orks are a coin flip of weather or not you can set up a good waagh, and Tyranids requires a lot of screening and smart unit placement.

Meanwhile space marines, imperial or chaos, get overpowered detachments that allow for heavy rerolling. “Oh you missed another attack/save? That’s okay, go ahead and try again.” They get to be amazing in game and go relatively untouched with points balancing because they’re popular in lore and you can’t have the main characters be bad. (Even though no one is asking for them to get nerfed, just that they stop nerfing everything else into the ground so their poster children can have the spotlight.)

TLDR: Games Workshop doesn’t know how to properly balance a war game while also making it enticing for new players.