Huh?  None of the handful of consumer-land ISP's I've had since 2011 blocked incoming high ports by default.  Sounds to me like you are confused about the difference between 'contacting your ISP' and 'logging in to your router'.  Or you signed up for some kind of nanny-help-me add-on from your ISP.

It is worth note, however, that blocking a port is a triviality from a network engineering point of view.  I would guess that at this point even if there are any more mom-n-pop ISP's left they would have the equipment installed which could do this (among other things) and if they don't they would be required to give some rack space to the feds to install such a thing.  The calls for an 'internet kill switch' from the fasciests running the show here in the U.S. (e.g., Lieberman, Feinstein, Rogers, etc, etc) have pretty well gone away telling me that it is firmly in place.  It would not 'kill' the internet (which would cost the mega-corporation who own the politicians money) but it would change the internet significantly at the flick of a switch.

Now deep packet inspection and traffic shaping is a little bit more involved.  That said, 10 years ago Comcast was doing it with apparent ease on one of the busiest consumer networks in existence.  They were specifically shaping peer-2-peer traffic since it was costing them money.  They got in some minor trouble for it with the (now defunct) 'net neutrality', but I sense that they quite mostly for economic reasons when they got more fiber buried.

Beyond that is actual packet manipulations.  Like grabbing an http stream, opening it up and slipping in an http header element.  That is fun and useful.  Related is just recognizing and diverting a stream.  I know my ISP is set up to do it because I had an unusual 'outage' some months ago and when the got me 'fixed', all http and https traffic was being re-directed to a page telling me that my Dish networks account needed attention.  I don't and never did have anything to do with Dish networks so this was an amusing little slip-up to me.  --edit:  No, it was NOT a DNS redirect.

All that is to say, if Bitcoin's claim to value rests on the kindness and protection of the proverbial TPTB, and the perceived technical difficulty of having the global internet be anything but 'neutral', I'd consider the value proposition to be not all that high.  And THAT is why it is critical to me that the solution remain 'agile' whether it happens to need to be at this point or not.