I also don't think consent is the right basis to use all the time (however it's important to note that no lawful basis takes precedence over any other) and good vetted vital interests and a contractual agreement is preferable, however consent is the easy way out.
"This is what we do do you agree: yes/no" is much easier than to develop a valid vital 1st and 3rd party interest for each case and most online services don't require a contract.
However the idea that somehow you have to provide services to people who do not consent is simply false.
That you can't do is tie completely unrelated interests to a single consent for example:
I have a website that shows you local events and allows you to sign up for them, my business model is to sell your contact details to promoters.
If you do not consent there is no reason under the GDPR to compel me to provide you with a service that costs me money to run while you refuse to participate in my revenu stream.
What I can't do is say if I run a ticket website to refuse to sell you a ticket if you do not consent to me using the details you've put into in order to purchase them to be sold to promoters or in other words under the GDPR the information collected for the purpose of selling you a ticket cannot be used for another purpose selling your info to promoters.
It's also important to note that in some cases the "I agree" isn't actually used for consent it's just a UX quirk, you can still allow people to opt out even if you don't use consent as the lawful basis for example I can display you the following message:
"I collect the following information: XYZ, and issue the following tracking cookies: ZYX the lawful basis for this is the vital interest of my company and my business partners"
I still technically need to give you a way to opt out, so the windows that says opt-out or agree isn't necessarily a consent window from a GDPR point of view.
And as previously mentioned I can deny a service to you if you opt-out because I can't monetize you in which case I can legally redirect you to a page that says you can't access by website until you agree to my terms, in this case again consent is not necessarily a lawful basis rather than you acknowledging the lawful basis i presented under my terms of service.