I agree with you. The last 6 new engines I've purchased are all Rail King for the very reasons you cite. I just had to get over the mental block of adding DCS to my new, in-progress layout rather than limiting to TMCC like my prior layout.
When I said equivalent, I didn't mean in quality, detail, or caliber. I meant that Lionel Traditional and WBB already offer most of the same models even if less caliber. Rail King has a Berk, Lionel Traditional has two non-scale Berks and WBB has one. Lionel Traditional has a K4 coming out in LC+2, WBB has semi-scale Pacifics/K4s.
Go up and down the roster of Rail King steam, diesel, freight cars, and passenger cars, and I think there are very few, if any, models that Lionel or WBB will say "I need to add that to our roster to fill a gaping hole." WBB and Lionel already have semi-scale molds for NW-2s, GPs, F3s, FAs in 2 sizes, GG1s, FMs, Hudsons, small steam switchers, and Mikados.
Perhaps WBB decides to add some articulated steam from Rail King.
Anyway, fun to speculate. It's that time of year for prognosticating....NFL Draft, March Madness, and 3RO hobby.
Speculation is definitely fun. I will have to take my yearly March madness break from watching hockey.