My fingerprint scanner is effectively my on button. I’m not snaking my finger up the side only to start swiping in the area my fingerprint scanner is in anyway. It’s perfectly accurate and fast, and when I grab my phone my thumb is on the scanner before I’ve even pulled it out of my pocket. The vibration feedback when scanning starts and finishes is just fine, something I can’t say of my laptop.
If you’re someone who often breaks their phones, I can get the screen crack argument, but I’ve never had that issue. I don’t know why a broken phone couldn’t break the power button as well, though; if that’s a concern, you’d probably want a phone with a scanner on the back. I don’t have any issues with rain either (though that doesn’t matter because the screen is inoperable when it rains anyway).
It sounds to me like you’ve experienced a bad fingerprint scanner or maybe just a bad phone in general.