I have the old UI maybe? Or the new one? I can't keep up...

I just have a "Report Spam" icon, with no choice to differentiate between the two.

It's an interactive prompt once you press the spam button. Whether it appears depends on whether the system identifies an unsubscribe link in the mail.

I'm always worried that the spammer just uses "unsubscribe" as a sign that the email actually got through the spam filter and a human saw it?

Aside, I've been having a TON of very similar spam emails getting through Google's spam filter, and even marking them as spam doesn't seem to do anything. It's been going on for months at this point. I'm close to just closing that Gmail account because I have no idea what to do about getting close to 10 spam emails per day straight into my inbox in a way Google seemingly can't fix.

It's super obvious spam too. "tHe IRs hs a REFUND for u" level stuff.

Wouldn't it be better for Google to have a "mark as spam and delete future emails" option? That way, your inbox stays clean, spammers have wasted some credit for whatever email marketing service they use on an email that will never be read, and eventually spamming would become futile since emails will be deleted on reception.