Off grid you need batteries. You can run the gen to recharge them to about 90% of full but not to get them full, which takes "forever" way to long to run the gen for the 90 to 100 part.
You can't keep doing 50-90s because of progressive capacity loss each cycle from not getting to 100% each cycle. After several 50-90s you must go to 100 to "recover" the batteries. Then you can start over.
Two ways to get to 100%: Shore Power for a day or Solar if enough sunshine before you draw the batteries down again. Or go split bank and get half the batteries to 100 while running on the other half.
So that is what solar is for, so you don't have to get shore power to get to 100 unless there isn't enough sun when you need to get the batteries to 100.
If you have to get full hook ups anyway to do laundry, sani, etc, and that also works out for when the batts need doing up, then you can skip the solar.
Having some solar means you have more flexibility in when you need hook-ups.