Had even half his voters, just in FL, gone to Gore in 2000

If half of his voters had gone to Gore and the other half gone to Bush, there would have been no difference. And Nader was quite popular among liberal Republicans (my own Sierra Club loving fiscally conservative father, included).

Past that, it was Pat Buchanan who had an unrealistically large number of votes in Florida, largely due to the construction of the "Butterfly Ballot" and the placement of Gore's name on the ticket. The whole argument over mispunched holes and hanging chads boiled down to whether a bunch of Gore votes were under-counted thanks to crooked Republican-aligned election workers.

And even if we scrape all the third-party candidates off the ticket in a straight up one-v-one contest, Al Gore's real sin was losing conservative Democrats to George Bush Jr by a 12-to-1 margin relative to Green defectors. He got Southern Strategy'd in the same way dozens of his down ticket Democrats got got during the 80s and 90s, and then again as the country lurched hard right in favor of Palin, Gingrich, and Trump in the run up to 2016.

And somehow we still have people preaching abstinence or a third party

The lesson that Democrats took away from 2000 was that you never actually have to appeal to progressives in your own party. Always, always, always sell out to corporate interests, and then just make "Compassionate Conservative" sounding noises to shut up your liberal base. Kerry, Obama, Hillary, and Biden all learned from the Gore playbook and adopted a purely rhetorical electoral strategy, while spending their working hours bailing out banks and big businesses, force-marching more troops across the Middle East, the Pacific Rim, and Latin America, and privatizing all of the essential New Deal / Great Society social programs of the last century.

When Joe Biden's platform is to the right of Ronald Reagan's, what the hell is a progressive to do? Keep voting along with the pack, so Biden's successor can lose to Ron DeSantis/Ted Cruz ticket in 2028?