No one said you have to test on everything. Just adjust your target and testing hardware to something midrange, maybe even budget optioned. As above, test on some mid-range or even budget-level 2015 hardware, laptop or phone, and if it's smooth on that, it'll be smooth for people running 2020 hardware. You can never be sure about the reverse.

That being said, there's a lot of crap software out there that's slow even on 2020 hardware.