My theory is that what they are adapting to is all the other mitigation measures that we've been doing for a while--think masks and social distancing.
Bacteria would have more options, since they're so much more complex. Viruses just don't have much they can do.
Of course they can. We have this pandemic because a coronavirus became highly transmissible.
These mutations are the virus finishing its adaptation to humans. It will eventually end up at a local maxima, just like, say, measles did.
There are many ways for this to happen, some of which covered in this thread - changes in the surface presented to the host, more viral load produced and expelled by an infected host earlier being some obvious ones.
Some potential methods that have occurred with other diseases in the past include additional methods of infecting hosts (from prior versions), such as viral envelopes that can insert against additional types of cells, or changes to the way the virus hijacks cell replication machinery to produce products that are better at hiding what is going on to the immune system.
The virus can't "evolve" its way around not reaching the host very well. Evolution isn't magic. The virus can't "evolve" teleportation or an immunity to high-energy electromagnetic radiation just because it would be really useful to it if it could. It can't just "evolve" its way around masks very well.
As I said, bacteria have at least more options, though they face the same physical constraints everything else in the universe does. Viruses don't really have many options. They are very simple.