I've had decent luck with same-day ADRs - you may not always get the place you've been dreaming of if it's popular, but there's usually something you can sneak into. Covid seems to have mixed things up - ADRs are much harder to get now with staffing shortages and restaurant closures. When I went in July, I booked 2 ADRs about a month in advance, then booked a third on same-day...the 4th night I just did quick-serve.
My next trip is September 24th and I looked this weekend to see if I could get any ADRs - some where available, but none were really convenient to the park I chose for each day, or the times weren't convenient (5pm or 10pm, nothing in between)...so at the moment, I have no ADRs and not really planning on booking any. I figure since this trip is during Food & Wine, I may just park-hop over to Epcot at the end of each evening and pick a few booths to visit for bites and drinks, and not bother with ADRs...or hop over to Disney Springs and see what I can walk into with a moderate wait. I will probably check for any ADRs that fit my schedule each morning before heading out, in case any have opened up for same-day.