To follow your example, changing falling rules on the fly is bad but if those rules had been changed before the campaign started by a DM whose game you were considering playing in, would it be a deal-breaker?
Not at all. Almost nothing is a deal-breaker for me. I can enjoy playing with all manner of DM styles and systems so long as I enjoy the company of the DM and players.
But when *I* am the DM, I see interpreting and applying the rules as a group activity that all players, not just the DM have a say in.
I homebrew much less than I used to because I'm more interested in playing and creating stories and worlds than I am in designing or tweaking systems. In the four years that I've been playing D&D I've moved more and more to just playing the RAW. It is easier. It is easier in part because I can then play with a group of people who all have equal access to the rules and who may even know the rules better than me. Homebrewing puts more burden on me as the DM to keep the rules in my head.
In my current game, my deviations from RAW are mostly selecting some of the rule variants from the DMG and using an altered inspiration setting inspired (ha!) by the Angry DM. All of these rules were circulated by e-mail to the players before the campaign started and they are written on the same whiteboard as my Wifi password.
That said, when it comes to changes to a published AP, I don't ask my players for permission. I'm running Curse of Strahd mostly RAW but I've integrated some ideas and content from material published in the DMs guild. I've also used crunch from Volo's guide with some of the encounters (mainly that relating to hags, which makes certain encounters deadlier). There is no way for me to run that by the players without spoiling the adventure. Instead, I state that I'm running X module/AP mostly by the book, but that I reserve the right to make some alterations. Or, I will say I'm running an adventure inspired by X but it is heavily customized.
Also, during games, rules discussions are quickly resolved. But between sessions, in preparing for some sessions, I may put hours into researching a rule. I may come back to the party saying "in the last session, I ruled X, but after studying it some more, I think it should be Y because of A, B, and C." I won't retcon the results of the "incorrect" ruling but the new ruling will be law going forward. If everyone disagrees, then I will go with group consensus.
I just do not like capriciousness in my games. It is not fair to the players.