Except for cookies are already transmitted to the client device in far too many cases before the disclaimer is displayed.
Also I'm not sure blanket agreeing to all (tracking)cookies will be in accordance with GDPR.
The implication is that, now that you know that cookies are used for tracking, remaining on the site is implied consent. Like the omnipresent "this call may be recorded" statement at call centers.
It is an instance of a much broader issue, where contracts are no longer the result of any negotiation, but are a take it or leave it option.
I understand going after each and every website would be impractical, but imo a disclaimer with a button - most probably after the fact the site already transmitted a handful of cookies - does not comply with the spirit of the regulation.