Why do dems pretend that they care about who the republicans nominate?

I am not a Democrat although the Republicans on here accuse me of that all the time. My reason is that as a former lifelong Republican I would love to see the party and its candidates go back to being the kind of party that I joined back in 1971, for the people, for the rights of citizens, Not what they are now, the shills for the super rich and huge corporations, the party of mean spirited bullies to whom no dirty trick is too low or slander is to vulgar.