I traveled 8 years 24/7 in a 28 foot Class C with no car.
However, I did add a bicycle at some point, then added baskets to bike and so on, even an electric kit, so if I was tired or over loaded or head winds were strong, I could have help with the push of a button.
I drove the camper where ever I wanted to go. Mostly I wanted to camp out in nature at far flung places, so I would shop and stock my provisions on days of travel so I arrived at camp with all I needed. Mostly when I got to camp, I focused on walking and biking. I cooked at home (in the RV) 99% of the time so I wasn't going out to eat.
My sightseeing interests was nature, so I wasn't really traveling to events either. I just wasn't interested in crowds. I liked to camp with water such as on lakes, rivers, canals or beaches.
I think uber is more of an urban thing for bigger cities and not prevalent in campground areas.
Initially I had thought that I could rent a car now and then to go shopping or sight seeing, but turns out the camps I preferred were far from car rental places and most only delivered in a tiny area, like anything within 5-10 minutes.
In 8 years, I only managed to rent a car twice. Once when my rig required all day repairs, it was 99F degrees and the shop offered a crummy waiting area. The rig had to be on a lift all day, so I couldn't lounge around in it (like I've managed to do at many repair places). Since I planned that big repair in advance, I did manage to get a car rental for the day worked out in advance.
The other time I rented a car, I had a friend with me and we got a car for a day or two but later we decided on future trips, it wasn't worth the hassle and expense, it was just easier to drive the RV to places and be willing to walk a lot after finding parking.
In one place, the island of Ocracoke,NC it was hot and I was having trouble walking and I had a friend with me. The island offered golf cart rentals that were legal to drive all over town, so I had a blast with the doggy and my friend, sightseeing with the golf cart all day.
I did take my RV to some interesting places. I managed to parallel park on the street near Niagara Falls and hike a mile or more to the falls and back. My rig took up two parking spaces end to end. I saw some historic towns on foot, after finding far flung parking for my rig. I traveled with a small dog who I often took on my walks about town or to the falls. While the falls offered satellite parking with shuttles to the falls, they wouldn't allow dogs on the shuttle, so I hunted around until I found parking where I could walk to the falls and take doggy with me.
Another time I went to pick up a friend at a historic train station. The only parking I could find to fit my rig was two parallel spots on the street. I had to keep feeding two meters because the train was way late. I entertained myself photographing the historic train station and walking about the area which luckily was in a pretty safe part of town.
If I was going to camp and go sightseeing by RV, I generally planned to arrive at the camp, then sightsee the next morning, then come back to camp and settle in for the remainder of my stay. Sometimes I showed up at camp early, checked in, but didn't set up camp, instead going sightseeing then coming back later to park and set up camp.
Much of my sightseeing at other places was planned on travel days. Short trips to the next campground with plenty of time to putter and stutter about stopping hitcher and yonder along the way.
I've actually managed to spend 9 hours doing only 60 miles (between camps) because I made many stops along the way. Many times I booked the maximum stay at the campground, mostly two weeks, if it was available and in a beautiful area. I seriously enjoyed sightseeing on my bicycle in flatter areas, not so much in the mountains.
So in other words, you may want to rethink your planning if you travel without a car. It's possible to do sightseeing with a bit of planning and a willingness to walk as convenient parking isn't always close by but it can be found. Sometimes it actually is close by in a parking lot. During the daytime, there's no hassle parking in public lots to go sightseeing, even if one needs extras spots to make room for the rig.
Most of my eating out, which was rare, was mostly done on travel days too.