There are a couple I have in mind. Like many techies, I am a huge fan of RSS for content distribution and XMPP for federated communication.
The really niche one I like is S-expressions as a data format and configuration in place of json, yaml, toml, etc.
I am a big fan of Plaintext formats, although I wish markdown had a few more features like tables.
Then don’t get me started about how the www subdomain itself no longer makes sense. I get that the system was designed long before HTTP and the WWW took over the internet as basically the default, but if we had known that in advance it would’ve made sense to not try to push www in front of all website domains throughout the 90"s and early 2000’s.
I have never understood why you can delegate a subdomain but not the root domain, I doubt it was a technical issue because they added support for it recently via SVCB
records (But maybe technical concerns were actually fixed in the decades since)