I think we’ve all been to WDW on days that have masses of people trudging to their ̶d̶o̶o̶m̶ fun, but still had a great trip.
Last year our Friday in MK was especially crowded, yet we hit all of the attractions we planned and didn’t wait more than 15 minutes for anything the entire trip (except for a last minute call on FEA after Illuminations since we had never been on it. It ended up being 30 minutes, which was fine.)
In fact, on that trip my DW started feeling bad for the masses of people as we kept scoring FPPs and strolling past queues of standby people starting into heat space.
There are certainly times when you have to punt the plan for a step or two (ride down, downpour, unexpected bus wait, etc) but with the tools in the Liner toolbox, there’s always a fun alternative to go for instead, even if it is just a Mickey pretzel and people watching.