But it's really disappointing that it needs a sign up. When quickly checking an address, it would be more helpful if it doesn't require a login.
I don't even know what this strange log in should achieve. I wouldn't mind to have ads on such a site, if the site wants to make a profit...

I agree that sign in with an account to use a block explorer is uncomfortable.
I tried searching and found most of websites that requires an account to use their forensic blockchain analysis. Two websites I can share, free to use, no sign in.
Four tabs: Address, Inflow, Outflow, Money flow:
https://explorer.bitquery.io/bitcoin/addresshttps://explorer.crystalblockchain.com with two features: Transaction history (need a Demo account to use Connections, Mentions tabs); Visualization (free to use)
https://explorer.crystalblockchain.com/address/https://explorer.crystalblockchain.com/visualization/new/Copy and paste an address at the end of url links to use.