Democracy involved compromise, unless you just wanted to be defeated in detail in the political arena. You may wish that boomers and their views didn't exist, but for as long as they do, they are a reality that needs to be faced.
If you just ignore them and push them towards the repub candidates, then it isn't progressives that win, but republicans. Who can then do away with democracy at some point and secure their position despite dwindling demographics, in classic Realpolitik fashion.
Gramps may not get all the nuances of the modern world, I doubt any 80+ yr old does, regardless of how good their briefings are. But he does understand why moderates are important. And he's good at diplomacy in general.
Yes the system sucks. This is not news to anyone already past their teenage years. It's what we got though, and to reform it, you need progressive politicians, which will need moderates in order to win vs entrenched repubs. Reality is a removed, and it doesn't treat purity very well.