Your points are well taken and generally valid. We can still work at the local and state levels to affect the outcome of elections in the flyover States and rural counties. The corruption in large metropolitan areas is so entrenched I don't think it can be corrected short of completely abandoning the present system. The effectiveness of local and state elections will depend on states being able and willing to exert their state's rights. A war was fought over this issue.
At the federal level election fraud has been perfected and will continue to be fine tuned since there is no penalty through the court system. This expertise will filter down to state and local elections unless stopped. We the people have become irrelevant and the election results depend on the majority of useful idiots doing what they are told in exchange for government benefits.
I think the Republican Party is pretty much done. For decades they have been on defense, never once making demands on the other side, always ready to give up ground to placate their enemy. I terminated my membership in the Arizona Cattle Growers Association for this very same reason. Their lobbyist would enter negotiations and the first thing he said was "this is what we are willing to concede."
Where we go from here remains to be seen. I see favorable conditions for a third party to be organized and eventually become influential but it will have to happen quickly because in one generation we will be a second or third world communist, socialist country.
FWIW, I see myself as a Libertarian more than a Republican. Maybe that's one small thing I can do, change my voter registration to Independent or Libertarian. If enough people did that it "might" send a message.