Twitter still exists. Renamed. Same exact thing. You can create an account and post whatever random things you want. Some people might follow you. Some might not. If you see something that makes you sad, you can block the person who posted the sad thing.
It very much is not. No third-party clients; can’t see threads without an account; owner inserting himself and his ideology at the centre; fewer and less diverse participating people; diminished trust in the platform; more spam; different verification rules… Even the character limit is different.
Not just aggregating data for fun. It made third-party clients like Tweetbot impossible. Similar to non-old.reddit.com, the web interface has been crappy for a pretty long time, but was easily worked around by using better clients.