You have no idea if the website will block your IP because some ban list contains your IP block because someone else in your city did something to get it there (such as hitting the ' key by accident). But you won't know until the end because they have not added the blocking functionality to the UI, but via a small amendment to the back end
Next, you will have to assume it needs email verification on top of the captcha. If you just enter a random email address that doesn't exist and hit the next step button, it may (99% likely) only then tell you to go check that inbox for a verification link. After this, it may ban you for trying the second registration too fast. So it's best to always use a temporary email
There may be a CPU or GPU intensive bottleneck on the website which immensely slows down this process. For example, the front page of Github with the 3D globe brings lower end machines to a halt
You must now follow these steps:
1 The form may not work at all due to requiring a specific browser or OS. This often is apparent by a button that you click and nothing happens so you will need to try a few browsers and maybe even OS or try switching your screen resolution. You may only get stuck N steps in and only find out then that you need to do this
2 Find temporary email and set up address on it. This may require a recaptcha which means 30 seconds of clicking images as they fade in very slowly. But your connection could drop or cut in which case, the captcha will show an error box and you start over
3 Redo the signup form because it will say your password doesn't match the password policy (each of which is completely different for every site). 50% chance new captcha
4 If youre lucky the website will only require a user name and password. However it may ask up to 10 irrelevant questions depending on how pretentious the administrator is
5 The site may block the email provider, or the email provider blocks the sites. go back to step 1 and find a new email provider, but then the site might block you or escalate to SMS verification
The signup form could have multiple pages, and each time you click next there is an opportunity to badly handle connection loss or ban because some of the data transmitted was not as expected, or similar issues as one would expect of amateur code
if you activated the captcha before going out and setting up your email and come back, it may have expired. the login page may itself expire as well by the time you come back to it. we still didnt mention browser addons, which square once or twice more (missing DOM elements causing malfunction, XSS filtering breaking the page, ad blocker blocking, etc). the browser may ask to restart to apply an update when you open the tab for the email website (recent Firefox issue) and you start from scratch. some of these are avoided by having the concept of a single email address that you use for everything or 50% of everything, but it will get spammed and shared and may be or blocked or become so because you shared it too much
How low-end are you talking about ? I have a fairly low-end laptop that's more than 4 years old and it works fine.
As for the rest of what you're describing, it's nothing like my experience of the web, though some government web sites come close.