Not really - if all of your devices use WPA3 the attacker won't be able to brute force your password for example. You might think "if all your devices support WPA3 then why not disable WPA2?". The obvious reason is you might occasionally want to use WPA2 without fiddling around with router settings, e.g. if guests want to use your WiFi without recompiling their phone's kernel.
Then another obvious but naive response is "then your security is no better than WPA2 anyway" but hopefully it's clear why that isn't the case in the real world.
I mean from a security standpoint you're right, but having opportunistic WPA3 seems to be the only sensible way to deploy until you reach acceptable device support.