Yeah. Honestly I think that's the one issue we can agree on with the whole mandatory range segregation GW has. Especially since you only really see promotion of kitbashing in the youtube community and other communities centered around modeling. With the gaming side of the community you don't really get that much.
So there really isn't much incentive for a 40k player to dive into other ranges unless they want to invest in said ranges. Like I'm invested in 40k, HH, AoS, and Necromunda, and it costs a lot of money for that. At least with HH and Necromunda there is some overlap allowed. Though trying to make a HH squat army is EXPENSIVE given the amount of exo-squats needed to make one special unit per detatchment, that and not really having enough bolt guns per regular kit of Ironhead squats.
But getting back to the whole "range segregation causes more harm than good." I've definitely heard of custodes fans dreading the possibility that their range refresh is going to be exclusively locked to the HH era with no guaruntee that Heresy Era units already in legends will carry over next edition. And that's just one example. I've also heard lots about Admech fans wishing they were able to play Mechanicum units in their armies since all they got recently is a servitor killteam and inspector gadget sniper.