Or when “log in” Is hidden in a menu, while “sign up” Is a nice clear button on the home page.

A real middle finger to existing customers. It's so instantly and visibly rude.

Or far away. Or using some "clever" non-signup word like "Already in the beta? Click here."

I started using uBlock Origin’s picker tool to block those buttons and other signup/engagement prompts on websites I frequently visit or already have accounts with.

Manually hiding certain elements can make a big difference and I highly encourage trying it out.