I tried searching for this issue but couldn't find a duplicate.

Effectively, the block cursor has been practically illegible for the game's existence, and especially with high density displays, this issue is only getting worse.

The block cursor is always black with lines one pixel or two pixels large-- not Minecraft pixels (1/16m), but pixels on the physical screen. This is especially difficult to read on dark blocks, but in general, you have to squint to see it, especially when counting blocks.

I've attached some images of the block cursor, one on obsidian, and one on dirt next to some grass. The outline on the dirt is faint, and the outline on obsidian is effectively invisible.

Having either more contrast on the cursor and/or more thickness feels necessary to ensure it's visible.