I don't know if there are Uber/Lyft drivers in Seward as I usually drive down. The town is small enough that you can walk everywhere, I think I've only driven to one location across town and that's because I didn't want to carry the groceries back to the campground. I don't recall seeing any taxi's, but they could be there by now. Should there be taxi's, it's likely run by individuals who will fill the car along the route. So unless you and your group fill the vehicle, it could take a while to get where you are going.
Most rental companies sold off their fleets expecting to replace the cars at the start of last season, then COVID hit and no visitors came, so purchases were put on hold. Now they can't fill the orders, which is a common thing across the country right now. We have been less traveled, but things are starting to pickup now that our goobiner removed requirements for testing and quarantine on all incoming visitors. You can voluntarily test upon arrival, but it's up to the traveler to make that decision.
If I had to choose between McKinley Village or Glitter Gulch (just outside Denali Park), I'd go with Glitter Gulch. The views of Denali (Mt. McKinley) can be better from McKinley village, but all the tourism crap is in Glitter Gulch. I typically camp in the park itself when I'm not driving through. It is ultimately which location you stay in, both have rail access for the train. The white water rafting down that section of the Nenana river is great as well; you get to enjoy some class 3-4 white water.