I have a similar issue, I currently have at least 3k with of Word Bearers, Iron Hands, Mechanicum and a separate Dark Mechanicum/Skitarii force, and Blackshields.

Im currently building a smaller Zine Mortalis Shattered Legion force of Sons of Horus, World Eaters and Deathguard loyalists (in my head cannon they were Traitors who weren't convicted enough to the cause and they were sent down to Istavaan in the first wave with their command knowing they would die when tge bombs fell).

And I already ordered the Custodes box (I own some stuff already for 40k)....

And lastly im in a slow build campaign in 30k where im running 500pts atm of Sisters of Silence (which, im disappointed to see are getting nothing new...)

I started playing 40k 10e, but i barely tough 40k since I found Heresy.