What's taking so long?
I'm guessing that 50% of page load time comes from these shit tracking scripts but what hasn't been mentioned is the other half (well, 49%). I propose that the other part of the equation is security, mainly SSL/TLS handshake, authentication cert download, multiple session encryption renegotiations. This depends on the website, but a lot of mainstream websites need good protection. HTTPS is a good thing but it comes at a price.
As for 'it's your fault, developers' I don't know about that. If you want a quick and dirty website you'll go to Wix or some canned wordpress theme and ya gets what ya get, no tweaking allowed. I got off the phone with a Google Ads rep yesterday after she stepped me through changing my paid ad campaigns. I'm not using tagged advertising but it's pretty easy to see how someone could have a lot of slop code running on their website without knowing it.