This issue of selection responsiveness has come up recently over at Polycount as well:
I agree that it is a big problem, which I noticed immediately upon switching over to 2.8. I can understand why it may not be considered a bug, but it is still a pretty huge design issue with the default keymap that I think should be addressed. The responsiveness of Blender’s modeling tools has been one of its greatest strengths. For such a huge regression in this area to be considered the intended behavior of its default configuration is a mistake.
@brecht @pablovazquez Can we get a response to the solutions presented by @1D_Inc? If testing proves that there is little conflicting behavior from these changes, they should be adopted as soon as possible.