We were at the parks March 4-8 then again on March 11-13. I cannot complain about the weather as that was great on the days we were there. But it was MUCH more crowded than I was expecting and sites like TP had predicted. I have gone a couple times in late March in the heart of Spring Break and it was
not this crowded.
Unlike the OP, we did not have any problems with ADRs. I had 1 or 2 each day and we were always seated and served in a timely manner. But the lines for rides? Yowza!
FWIW, I was able to get a 4th and even 5th FP at all of the parks. There was just DW and I and that made it easier. At Epcot we even got FEA as a 4th FP when someone canceled. After that I got another Soarin FP for a 5th FP.
This past Monday we went to Epcot and got to the IG at 8:45AM with the goal of riding TT first thru Standby. No it was not an EMH morning. I always avoid EMH parks. Like our other day at Epcot (on March 5) they let guests in early and started the rides early. By the time we got to TT it was 8:55 and TT was up and running and the line was moving (and all the way out to Innoventions). We waited
40 minutes to get on the ride.

Yes really. And it was not broken down. Just REALLY long.
Put all that together and we still had a great trip. I was just expecting lower crowds.