At face value the question is easy - yes, you can Uber from FLL to Miami.
There are a lot of gaps that might need to be filled in to best understand your experience doing that trip. Just sharing a couple of thoughts to try and help you quantify the value of using FLL for yourself. All of my comments are pre-COVID so things maybe different.
- Traffic - South Florida traffic can be bad and unpredictable. If you are doing same day flights (in or out) give yourself a little buffer. Most of the time things should be reasonable but I personally have been in long delays and backups at all sorts of hours, including the usual rush hours.
- Airport -pre-COVID I had to travel a lot for work (120+ flight a year) and FLL is one of my least favorite airports and gets poor ratings from others too (TPG). It is not as easy to navigate, and has slow security which are key issues among other things . It works but if that matters to you it could lead to more anxiety or frustration.
- Hotels - if you are avoiding rushing/traffic by flying in the day before, some of the hotels can be great bargains but are not as nice. Ones on the water are nice but can be expensive. The HGI just south of the airport is a good balance. Once before a flight out I stayed near the airport (hotel name withheld), and got woken at 3 AM by a bunch of noise. Looked out the peephole but saw nothing. Next morning found blood on my door and down the hall. Told the front desk at checkout and they said “oh, we thought we got it all”.