I went at the end of August last year and my then DH said "we don't need no stinkin ADRs." I made a couple anyway because I wanted to eat at certain places and I had planned his birthday. Well, We did eat a fair number of TS restaurants without ressies, but then we don't eat at "normal" times, but I was really glad that I had made ADRs for the two places I really wanted to eat. You can get TS food but it may not be at the time you want to eat. Also, you can make ressies from your resort when you are there. If they have an opening, they will let you know.
With saying all that, I would highly recommend making at least a couple ADRs at places you really want to try.