Your baseball or basketball uniform wouldn’t bother me in the least. Maybe shower if you just played your game and if you’re all sweaty

but I can withstand it if you need to get right to Mass. I can withstand quite a bit when my focus is squarely on Whom I am worshiping. See for example. It’s not going to phase me if someone walks into church barefooted. I know Jesus would not have turned that person away. So if He would not have turned that person away, whom am I to be bothered if someone comes in flip flops.

I’m just rejoicing they are there!
To your 2nd question, we wouldn’t if it meant risking our jobs and if we didn’t want to take that risk. However…
That said, before you nail me let me continue my answer to your question by also saying my belief totally rejects that comparison as nothing more than apples and oranges. There is not an ounce of fiber in my body, bones, mind, or soul that in any way believes we risk salvation by disobeying a priest’s dress code and wearing the shorts I wear. But if the Church wants to embark on a worldwide dress code with a ban on decent looking shorts and claim infallibilty on this issue, and if they want to excommnicate me for wearing shorts, then no offense but sorry that will then be when I become certain the CC is not the only one true Church on earth.
A priest in TEC tradition once told me and it is indeed my belief… “No one cares about how you are dressed on the outside. It is the opening of our hearts to God on the inside that matters.”
Translated… God doesn’t care what’s on your shoulders when you’re on vacation visiting in St Peter’s Square. God cares about what’s on your heart.
Hope that helps. That’s my belief. God bless you on your faith journey and peace!