You're fatally confusing Nader with a standard Democratic politico.
Nader's an activist. He sees a problem and bulldogs the public and powers-that-be into addressing it. Politicians have to compromise and logroll to get consensus, something that Ralph would do when he took up folk dancing and publicly puffing a blunt. Nader has
zero bend in him. I respect and admire him for tackling things with brio and zeal and usually some solid facts, but even when I agree with him in principle he makes some face-palm-worthy gaffes turning off potential supporters for being insufficiently pure in heart.
Nader went Green b/c he felt the Democratic Party had gotten too much in bed with Wall Street and in effect become GOP-Lite. FWIW I agree with him 100% on that score. I don't agree with tipping the election to W, seeing the results of W's regime over eight years.
Nader'd gotten into some spectacular pissing matches with Democratic insiders even during the Carter Administration and called out Clinton as a sellout of the first water, so the DNC would
never support him. Nader knew he'd go absolutely nowhere as a Democrat. Even Dennis Kucinich could get a little floor time at the convention pushing for plank #1278 on the platform, but Ralph? NFW.
OTL he made his point. He wanted the DNC to quit acting like progressives are votes already in the bag for Dems. Gore ran a rather moribund campaign and was orphaned from Clinton's active support so what should have been a walk for him was enough of a squeaker we were looking through mailbags for Florida absentee votes.

We all know how that worked out.
Could Nader have hectored from the sidelines and made that impact?
Nope. DNC would've yawned and dismissed his critiques as they had for the last twenty years. Status quo would have rolled on.
Gore would have gotten the nom. I liked Bradley and it was shame he ran into the brick wall he did in the 2000 campaign. If he were veep instead of Lieberman, you'd have seen a tad more enthusiasm in the general election IMO, but again, it's the moribund national campaign and fatally underestimating Bush that made it even close.
Nader had zip to do with both of those aspects so how much Gore's chances improve are tough to call.