I don't mean to pick on you but picturing the perspective behind this comment is very funny and a little sad to me.
grep is almost 40 years old. It is free software, fast, and doesn't share your data with anyone. Small knowledge of the file structure of MIME enables more advanced search. This is all without mentioning desktop-based email clients.
Reading your comment, I can only picture some web-page javascript-based track-you-and-show-ads 15-employee company whom you give your email password so they can connect to another service and make high-latency queries on your behalf.
Shows how far we've come?
Just exclude Mail from Spotlight search in Settings.
Well... this is why you might want it. Your data under your control. Your choice of tools.
If you're using GMail and Google decides to turn GMail to crap, well, bad luck.
Seriously, this is egregious. You rely on your email provider to accurately search your inbox - some emails are important business, tax, and legal documents that are relevant for years, even decades. Or at least be fucking transparent about the fact that you are not really searching all emails. I know Gmail is a free service and in the T&C you agreed to (figuratively) sell your soul but this has huge real-life implications.