Instead of responding to a bunch of stuff in pedantic detail, I'd like to try and clarify something. When I mention 'structures' or 'procedures', I'm thinking about recurrent processes that 'loop'. Play loops, right?
So, yes, I as a DM need to make a call about how long it takes for fire to burn through a rope bridge the PCs are standing on, or whether someone can jump across a chasm while wearing soaking wet armour. These kinds of rulings are completely normal in D&D, and I'm pretty comfortable making them, because they don't come up too often, and repeat even less.
(though, for example, some kind of flexible rule for counting down until something burns/explodes/whatever would be lovely, and indeed this is something I have a little houserule for).
The real difficulty comes from the stuff that repeats. If you're doing a piracy campaign, you're going to want to have some idea about how to handle naval battles and swashbuckling -- the odd judement call isn't going to cut it. The mental overhead is too much, and pretty soon you'll rule youself into a corner.
The other problem is: as a DM or GM, I want my players to be able to make informed choices about tactics, and meaningful decisions about what they do with their characters. If they're in a naval battle, they need to have some idea of their odds against that man-o'-war, and the risks involved in fighting it. If I'm winging everything, I have much less ability to provide that information.