There is a ton of external wiring and plumbing connecting modules, so it isn't as easy as undocking one. Think about all the power and cooling connections that have to route to the truss, plus all the data lines between modules. The US segment and Russian segment are inextricably linked with all those external connections, and potentially even cold welded together at the mechanical interface.

The maintenance is piling up on old parts. One of the selling points of new stations is to dramatically reduce the part count. Imagine stocking dozens of types of fans, fasteners, pipe fittings, connectors, etc for a bunch of different heritage modules.

Companies building new stations don't want the old stuff. NASA asked them. Even cargo modules, like Leonardo, which is basically a can, aren't desirable. At some point (idk if this is still true) Axiom was going to get the Raffaello cargo module out of storage on the ground to convert and reuse it, but that's all I'm aware of.

This is amazing and all, but I don't want this now. I don't want this under the current administration who will find every way to siphon funds, muck it up, and somehow invade someone over it.

Let me tell you what that really means. Congress had pockets filled with contractor cash and passed bill. Contractor makes a shady agreement with someone at the top of the program making major decisions at NASA who immediately retires afterwards, that disables the agency's ability to perform at any useful capacity. The reason to outsiders will be based on some bullshit about intellectual property and data rights, but will make collaboration essentially impossible, and will be the cause of failure if it happens. It's almost like I've seen this too many times.

Sometimes if only one contractor is involved, it's not too bad. Get several primes together and now everyone is screwed because everything is a secret.

Not without funding and competent leadership

Probably more contracts for Elon Musk and to not let China have the only permanent moon base.