We had a car for our first trip (2014), and did not have one for our last trip (2017). We did do a one-day outing to Universal, and rented a car for 2 nights for that. Other than that we used the busses, which weren’t too bad. Sometimes there is a few minutes wait for one, but I figure we probably make up most of that by not having to park a car and get from the parking lot to the park entrance.
In Jan 2020, we are not going to rent at all. We have never experienced Uber/Lyft but are going to try it out for our Universal day this time, and possibly use it to get to the parks a couple of times, on the very early days.