"Putrid and inbred" correctly describes the DRM scheme. The game underneath that crud was trying to go way more in-depth by building a sim game out of an RTS engine. They wanted to, say, have Sims in your SimCity actually drive to work and back and get stuck in traffic jams. Problem is, the average computer in 2013 couldn't actually handle simulating that many units. This isn't inbreeding, this is being overambitious. Shooting for the moon, and landing not in the stars, but in the Salton Sea[0].

[0] I have no clue if any viable launch trajectories from Cape Canaveral support such an emergency landing.

I played many of them up to that point (even the SNES version), and 4 left a discernable source taste in my mouth. I could see the potential, and it was at times fun. But, for me personally, it just never hit the right notes to harmonize all of the good mechanic additions. I think part of it also was the more realistic progression you would follow (i.e. start with farms, work up to towns, etc.), but maybe I just never gave it a chance. I just expected a better version of 3.

But yeah, the successors to 4 were undoubtedly a dumpster fire.