Here's the user manual for the TP-Link AC2300 "Archer C7", as found in the google results:
https://static.tp-link.com/2019/201912/20191231/7106508598_A...
Step 2 of first time setup forces a default password change. There is no way around this step.
The defaults for the router also do not allow router access from the WAN port.
This means:
1) These routers all have secured passwords that are non-default.
2) These routers were deliberately placed on the internet by people that knew enough about them to do so.
Just because it's not how you would configure your router doesn't make it wrong. There are legit reasons to place a router on the internet, so long as it's secured properly... how else would you remotely manage a router at a different physical location, for instance.
__Lastly__ click "Next Page" on the OP search results. The estimated 7,000+ results becomes 21. Many of which are HN aggregators reporting on this thread here.
So... out of the possible millions of routers TP-Link has sold in this model line, less than 21 are on the public internet - many of which no longer load via IP address (indicating they are no longer publicly accessible), and the rest have professional CNAME's attached, indicating professional management.
Nothing here...