Yes, websites with heavy JavaScript really slow it down. The newest browser available for it is based on a very old version of Firefox.

https://github.com/classilla/tenfourfox/

Youtube is extremely slow, and it can only play back 360p or lower video smoothly. There is no hardware h.264 acceleration. “New” Reddit is also very slow. But old Reddit loads fine. Hacker news is very fast, loads as quickly as a modern computer.