Suppose, as a hypothetical, that I was ridiculously wealthy and had an axe to grind with the local telecom/cable companies. I want to completely circumvent them and just…“get to the internet” sans ISP. What technology would I need to make this happen? And just how impractical/expensive would it be?
Been there, did that… Twice. 
You have 2 problems. You need to get a connection to “the Internet” from somebody. They don’t give that away free*, so you need to pay someone and pick it up where they deliver it. Which leads to…
You have to have some way to get it from Point A to your place. To do this, you need to either contract with an entity that can do that (the telco, a CLEC, etc.) or you run your own cables. If you run your own cables, you need a place to put them. You can either negotiate with the entity that owns the poles / conduit (here it is $4.77 per phone pole per year, not including the cost to make room on the pole if that is needed), or you can work to convince the city government(s) that you should be allowed to dig up the street and build your own conduits.
Either way, it gets very expensive very fast. If you just want to run a web server or similar and don’t need a connection to your home / place of business, you can rent rack space at a colocation facility. You’ll pay for space (and usually power), but there are usually many providers in such facilities, all competing to sell you service. There may also be a monthly “cross-connect” fee charged by the facility to bring service from the provider to you (you can’t run your own wires there, either).
At the moment, I have fiber from 2 telcos and one fiber I ran myself coming into my house. One telco’s fiber is no longer used, but the other one and my own fiber are still used. There’s also an interstate conduit we built that runs under the street past my house, but doesn’t come in (we sold it when we sold the first company).
Overall, in most sane situations it makes more sense to buy the package deal (Internet service and delivery) from some entity that serves your area. Lots cheaper, and you won’t have to baby-sit telcos in the middle of the night to get them to fix an internal network problem of theirs that’s screwing up your connection.
- Well, at some point “they” do - when you’re big enough to join the club and “peer” instead of purchasing connectivity. The variety of attitudes toward peering mean that you’ll still need to purchase transit from somebody, at least until you get to be the size of (for example) Comcast.
It’s an interesting question, I’ll take a shot. Bottom line is you need an ISP. Even ISPs need ISPs. There’s the Internet backbone, the economies of which I’m not too clear on but only has a few key players, and then a complicated hierarchical structure of ISPs. These “are the Internet” too.
You can become an ISP of one customer if you’re ridiculously wealthy and wish to burn some money. What that entails technically is a dedicated line to another entity who can route your traffic, some address space and some more or less sophisticated routers, nothing too extravagant for a small network. Probably there would be bureaucratic hurdles too but nothing money won’t overcome.