I agree. Obviously increased attendance has an effect. Sorry, not nitpicking here or trying to make a counterpoint, but that's actually a 36.4% increase in attendance. Even with a 36% increase though, that would take a 20 min standby line and make it 27 min, or round up to 30 on average... not 90 min for every ride. The real issue is that they let approximately 4 or 5 people from FP in for every 1 in Standby. Of course that's going to push a 20 min line to 90 mins! It's awful. What's the point of zooming to the front of the line on some rides, then waiting forever for others.I suspect it's both. MK attendance totaled 15.4 million in 2000 and just under 21 million in 2018, an increase of over 25%. That's an extra 5 million people or an extra 15,000 per day. Now the park has expanded since then. There are attractions that eat crowds, but the walkways feel that impact. Classic attractions feel that impact.
Conversely, does FP+ have an impact? I'm sure Disney has stats that say one way or the other, but my personal experience, anecdotal as it may be, is that when Fast Pass is not available for whatever reason, standby lines move faster. Logically, it makes sense. If the CM doesn't have to juggle 2 lines and give preference to the Fast Pass line, the standby line would move faster.
FP just needs to go away. It's an awful system giving people a sense of entitlement. It also makes the situation hyper competitive. Great, you know the system so much better than everyone else that the rest of us have to stand around forever. You're so much more important. Gone are the days of "Hey look! The Pirates line is down to 20 mins! Let's jump on!" It sucks. Once upon a time through pure luck you used to find yourself with a nice little surprise like that and felt like you just found a $20 bill on ground with no one around. With FP people waiting in standby feel like FP folk just stuck their hand in their pocket and stole a $100 bill.