OP, I was doing the math a few months back because offsite was so much less expensive, and I loved our offsite stay a couple of years ago. But we had a rental car then for a longer trip, and once I started adding in the cost of rental, my savings were pretty much obliterated.
If you have your own car, staying offsite makes sense. Parking costs are usually less (often quite a bit less) than the difference in on-site vs off-site prices. Plus, you'll be easily able to access offsite restaurants (usually less expensive than comparable Disney dining) and/or prepare you own food for more substantial savings.
If you are comfortable with uber/lyft, and don't plan to come/go frequently in the parks, you can probably come out ahead staying off site. Obviously, the more you come and go, the more the price adds up, but if you're going to the parks, staying for the day, and going back at night, you'll still probably come out ahead. Plus, you'll likely also get more for your dollar offsite. You forego some of the offsite savings because you'll be paying to come and go to offsite restaurants, but if you prepare some of your own food, you can still save a lot for the cost of a grocery run.