You do realise that they have three major titles on four platforms PC, XBOX, PS4, Mac (well, 3.5 since Mac release died in childhood) to handle and that ED itself is split between two versions Horizons and Vanilla Dangerous.
If you've seen the pace at which Planet Coaster moved from concept to full product, you'll realise where all the dev effort went for a year and a half... Now, I'm quite certain that that same amount of effort is now being channeled into bringing Jurassic World to life.
And since so many players have already purchased ED and many purchased LTSP there is far less incentive for them to spend the majority of their dev hours on a game that has already seen Peak Profit.
Companies owe it to their shareholders to chase the biggest profits and a massive title like Jurassic World is likely the biggest income driver for them in the two to three years once they open the Alpha, Premium Alpha, Beta, Premium Beta, Gamma, Life Time Pass, T-Rex Edition, Brontosaurus Package... etc...
TLDR
I'm disappointed, but not surprised at the rate of dev work considering the self imposed complexity FDEV have placed upon themselves and the likelyhood that JW will become their primary income driving franchise.
I said it begs the question, clearly there is an answer and it could be one of your assumptions, of course. But we don't know, and I would like to.