Text is always tricky in Unity. I have the same problem with a non-pixel font in a standalone build. Very annoying, especially if the sprites look otherwise crispy, and when you are not sure anymore if the problem is in the game or if it’s your eyes. I figured that pixel fonts were easier to render.
You could try to increase the font size. See here.
I tried this:
I’m not sure, though, if this will help because you generate a font atlas, which is a texture. However, somebody under this video stated that increasing the font size had worked for him.
If nothing works, create sprites for your text like you did with “Subshooter”. This might not be the best solution but you do not have much text, so it’s just a few kb of additional files in your project.
I successfully build your game to WebGL in Unity 2019.3.6f1. The result looks fine.
(Click on the image.)
“Pixel Perfect” is not enabled. The rest is as described, except for the button sprites because I didn’t save the changes last time. The glyphs of “Start” look crispy.
“Created By Mulligamez” has got the wrong shader in the TMP component in the screenshot. I don’t remember if I accidentally changed it. The shader must be set to this one: