That’s because drag selection support is removed from LCS, so it became that clunky.
https://developer.blender.org/T70645#792905
Tweak tool seems to be perfect paradigm for proper behavior, but, it seems, it just duplicates box select tool behavior without actually box selecting ability.
Currently you must hold the mouse still while clicking LMB in order to select the vertex.
It also doesnot tweak on blank space, just removes a selection.
I agree, current behavior destroys Blender usability to the core.
It is still deadly workflow issue, and one of the reasons our company declined Blender 2.8X for production cycle. It is just unacceptable to lose almost half of speed on misclicks and selection declines during complex organic modeling and retopology.
When this is fixed, we will be able to perform organic modeling and retopology in 2.8X, which almost entirely consists of selecting and tweaking vertices.
But it works for not complex scenes. That means - for 95% of the modeling work.
Combining a complex scene is just a final stage of a production cycle, not the only.