I found for myself that "compact" version of the new UI is not compact enough. And the only way around this is to reduce IDE's font size, which worsens readability.
Same here, if your "compact" mode is way less compact than what you had before you're doing it wrong Jetbrains. Information density is key when developing
for me it strikes the right balance between enough "white space" and density. E.g. VS code is not dense enough for me.
VSCode's file explorer tree is way too dense, though, the indents are not big enough by default