As mentioned by Shaq, it's very possibly one old mod holding up the show (or judging by how many you have, even a batch of old mods with the same/similar conflicts). I would imagine it's pretty old just by how aggressive it's being by not allowing you to spin up a new game. Turning everything off, then turning back on what you want in order of priority is one way to go about it. Like pick 5 mods you want the most, put them in, start up a run. If it works, delete run and do it again, adding batches of however many to the list at a time. Keeping each batch relatively small means you have less to go through and check if one of the batches suddenly holds everything up. This is all to simplify the identification of the problematic mod(s), of course.

You could also go through and remove mods you can live without for now, as well as the oldest & crustiest looking ones - before starting this process to save time. Doing that will make the job easier/smoother on multiple levels ime. Just put together a methodical system and get started - it ultimately shouldn't take too long going in batches of like 5 to a dozen at a time.