• it's a failing platform run by one of the most chaotic people in existence; everything you make there will literally or figuratively go up in smoke, from the posts to the connections
• everything you make there is currently lining the pockets of a racist, lying nationalist
• it's losing money at an alarming rate while being beholden to the debt caused by the leveraged buyout that sold out to the aforementioned chaotic bro, meaning that they're increasingly desperate to make money and will take more and more morally dubious deals in order to stay afloat
• the racism is a feature, not a bug, tacitly and overtly endorsed by the current owner
• the misinformation is a feature, not a bug, tacitly and overtly endorsed by the current owner
• the nationalism is a feature, not a bug, tacitly and overtly endorsed by the current owner
• they're systematically stripping user control and transparency out of the platform, from ads and targeting to user blocking to outgoing links
• they're absolutely going to keep putting every useful feature behind Twitter Blue or whatever they're calling it these days
• uptime might be stable for now, but as soon as more bills become due it's going to tank again
• a venerable and respected platform has been reduced to this in a matter of months because of one man's ego and hubris
• the longer you delay in building a new platform and new habits only makes it harder for you to do so when all this finally does become too much for you

These are only eleven reasons. I have many more, some personal and some universal. If at all possible, get off of Twitter.