Slow internet on fast TX rate WiFi

Head Scratcher with Apple router:

2.4Ghz wifi TX rate is 217Mbps. The Internet speed test is 20-30Mbps, we pay for 100Mb.

5GHz is fine though, full speed.

I even bought a 50ft ethernet cable and ran the TimeCapsule outside in the middle of the backyard as well as basement and stood at different distances to try and get rid of interference.

We have a few smart home products and such so there are almost 20 different devices that connect to this, only a few use 5ghz. I have noticed that the internet has been a little laggy lately unless I switch to the 5ghz.

I changed the password to kill the connection to all of our devices at once and still, the internet is much slower than what my MacBook shows what my TX rate is.

I have tested one by one, two iPhones, two MacBooks, and an iMac, all slow on 2.4Ghz.

Does anyone else have this issue with 2.4ghz?