I doubt those will fix the issues.
A better route can lower costs, but there are places in the world that build on much worse land for less.
Lower speed is unlikely to change anything, you can have a few sharper corners, but nothing that is a big deal. Meanwhile lower speed makes this much less useful vs flying. (and starts to make driving competitive - at least you have your car when you get there)
CA (and the US) has issues, and I don't know what they are. Every time someone suggests something they feel like a drop in the bucket, and all the different drops don't add up to much.
Land acquisition costs are one issue. The California Environment Quality Act (CEQA) is another. While well intentioned, it allows almost anyone to tie up any development project in court indefinitely based on trivial concerns. If we want to have a functioning industrial economy then we're going to have to scale back CEQA and accept a certain amount of environmental damage.
Your understanding of how the route affects the price is misguided.
It has nothing (or very very little) to do with how difficult the terrain is to navigate, it has everything to do with who owns the land, and how much they want to charge for it.
Often these "owners" only purchase the land once informed that it is a potential high speed rail route.
They will do the same to a different route. Once you buy land you become committed to a route. Reform is needed, but I'm not sure what.
In a way, it’s a transfer of wealth from masses to these land owners (or brokers in a sense).