It's definitely a power-user skill to be able to even recognize "oh, this functionality is probably broken because an extension is blocking a critical cookie/script or I clicked 'No' to the cookie banner".
Though I've noticed that sites that use cookie banners really do only put their ad/analytics cookies behind that gate. They don't tend to let you turn off, say, a shopping cart cookie with "No".
Well, I still think sometimes my AdBlocker is the issue when a site is not working, but when I disable it it still doesn't work so even for power-user is hard to know if an extension is breaking the site or not. This gets a lot harder when you use multiple such extensions.
