What the heck is going on??

If Cloudflare would be blocking your access due to suspicious activity, you would get a different response from Cloudflare. In the screenshot posted earlier it can be seen that the error originates from Garmin. I have also seen timeouts occurring between the Cloudflare servers and Garmin's servers. And as rockncrag also mentions, parts of Explore work while other parts keep loading.

So all this leads me to believe that the issue is at Garmin's end, either networking issues or performance issues.

Same here, quite anoying for such a service. Associated with the paid plans for an inreach for instance, it is not acceptable to disrupt the tracking just because of software/web issue. 
I have the same issues regardless of webbrowser, vpn or not, it is very frustating!
And the garmin website stating "everything is online and well" :-/

same here, and the rest of the family report the same. France here not working either.

Fully agree. In my case (from Spain) the Maps tab it is very unstable. Rarely works the web version, however from the app it works perfectly. The problem is that I want to load the GPXs from the computer. Very frustrating.

Don't try the new update app lol... it's as bad as the web explore now in my opinion...   I suspect like me all your planning and adding of pois etc is done on web explore as it is far easier with a large screen and a mouse..   But Garmin seem too not give a damn and fix the issues and instead they seem to be creating more!!

Whenever I open https://explore.garmin.com/Map, the menu consistently opens within 2-3s, which is indeed slow, but not unbearable. If you can't get it to load at all, then you could try to open the Console in DevTools (F12 in most browser), see what errors you get there, and then reporting it to the Support.

I get some errors there too, but they do not seem to prevent loading the menu:

Wow almost like I would never have done that before.... and even reported it... May be thats why we come to the forum too rant mate??

and just for you 

and thats not even the end of the list for explore....

The list is twice that and was even longer when I first email garmin support.

And just before you try saying try a different  browser etc.. Brave, edge, opera, Firefox  and chrome on any device and the same oes for tried multiple connects and device.... .

And still as of 1300hrs UK time(5hours+) this is and issue and I am on works Laptop on a completely different connection...  SO yet again this PROVES it is NOT device or Connection related and a Garmin server/site issue.. 

The same thing happens here. How can it state that "All Systems Operational" when all one sees is a spinning wheel?