Does the touch screen otherwise work just fine?
Did you recently do anything to your phone, like a major iPhone update or get a new case or screen protector that may be preventing you from getting your finger to the very bottom of the screen?
If you just recently did a major iOS update, you may need to get used to the newer gestures. I think it was between iOS 13 and iOS 14/15 where they changed it up a bit.
Switch apps on your iPhone, iPad, or iPod touch - Apple Support
If recently getting a new case or screen protector, you may need to take em off and test to see if that's the problem.
I just tested on my phone and there isn't a whole lot of wiggle room there.. I have to swipe up on the bottom ~1/8 inch or so of the screen.
Another thing you could try is Settings > Accessibility > Touch > Assistive Touch
Turn on Assistive Touch, it'll place a white dot on your screen that you can move around by tap/hold/dragging it.
In that same menu area, select Customize Top Level Menu.
Hit the minus sign until it says 1 icon. (you can play with more icons later)
Tap on the available function in the center of the greyed out area.. a list pops up.
You can select Home to get the functionality you want.
Press Done in the upper right.
now go into an app such as Safari. Tap that white floating button once and you should go to your Home Screen. Tap it twice and it should show the App Switcher..