My opinion......Security wise, the AirPorts are still OK general home use if you use a strong Wi-Fi password, but the guy that has to have the latest and greatest will probably disagree.
Keep in mind that even if you have a new router using WPA3 security, all of your Wi-Fi devices will need to have the same capability. Chances are, most of your other devices probably won't be able to handle WPA3 anyway.
If you are using the AirPort Extreme as the main DHCP and NAT router, top speeds are going be limited to about 325-350 Mbps, so if your provider is offering 1,000 Mbps or Gigabit speeds, the Airports will fall short in that category.
If the AirPort Extreme is used in Bridge Mode, it will handle up to 800-900 Mbps speeds.
The AirPort Express will be limited to 100 Mbps if it is connected using Ethernet, but it can deliver higher speeds if it is set up to act as a wireless extender for a network.
I still use two AirPort Extremes that are connected using Ethernet to deliver a Wi-Fi signal at a house that is about 2,000 square feet. I'll probably move up in the next few years, but there is no rush. The network easily outperforms the new "mesh" system at my next door neighbors house.......which has him scratching his head.
If you decide to replace the AirPorts, reset them back to factory defaults and take them to the local recycle place, the Apple Store or a Best Buy.
If you want to make a few bucks, you will have no trouble selling your AirPorts on eBay.