Wow, those people who keep their toothbrushes capped and out of the bathroom win another one. Never me, though. I'm a Hygiene Hypothesis Hoplite. Might well be a Semmelweis Simpleton though. Who can tell? Only time.
Like, I get it - it's gross. But humans can be exposed to a certain level of gross and not die, it's fine.
Not saying you should stick your toothbrush in the toilet, but unusually strict hygiene measures are unlikely to be net beneficial for you. My reading of the research is that greater exposure to bacteria is very healthy and desirable as much as possible without actually getting sick.
I'm reminded of this every time someone posts a link to FDA regulations of what is acceptable as "food", what level of contaminants are allowed in "food", and other things that really make you not want to eat "food".
That said, these practices do matter in other settings shared with strangers, so reflexive habits are worth having for that reason alone.