I've found calc's currency converter feature frightening.

Oof. That's a special kind of stupid. I get how it happened, but like, they found a way to make calc bad while also bringing an obscure feature in modern browsers I hate with a passion.

It reminds me of King of the Hill where Hank says "Can't you see you're not making Christianity better and you're only making rock music worse?"

One of the last straws that got me to migrate to Linux was how long it would take for calc.exe to open in Windows 10. Even on much older computers and much older version of Windows it was instant. Suddenly in the mid-2010's the calculator is so bloated you have to wait a few seconds for it to load? Fuck off.

It didn't always take a long time to load, but often enough that it was noticeable and 'worrisome' for the future of Windows.