There are many sites that are using captcha to protect their site, it is usually nused by legit site very well.

I am not a blockchain.com user again since many years ago, I do not know if the app or site do bring up captcha or not, but like you said, it is like it is new for you, likely you are accessing the site with with Tor or VPN. I do noticed especially when I am using VPN (which is the one I used often), there are many sites and even Google search engine that bring up captcha to solve, but while using my ISP for the internet connection, I see no captcha.

But you should know that you wallet is not hacked.