It's also not their job to know what I'm using to view their website. If my browser misrenders the page, that's on me. There are zero reasons to put such checks in place and lock people out for sending a "wrong" user-agent string.
The error message isn't "you have the wrong user-agent" and the recommended steps aren't "use official Chrome" though. These were all assumptions about the error the OP made other people here have already disproven.
All the error message says is to disable extensions or try a different browser. It doesn't say what went wrong and it certainly doesn't say anything about needing specific user-agents, hell it doesn't even recommend which browser to switch to it just says "try another browser". As someone already mentioned it's not the site's job to figure out how your browser loaded the page wrong just to tell you it did.
