Contesting without a team behind you is suicide. Whether you will have a team behind you at that specific moment in the game depends on how good your game sense is. Mostly this depends on whether your team is filtering in one by one. Going in solo and contesting a point is extremely risky because you have filtered in as one person versus 6, and I wouldn't recommend staying on point for long unless you're a Tracer god.

Waiting until a few teammates have a few ultimates ready and executing them in time for a push can work well if you have ground to make up.

Doing your job on your team is often more important than contesting point. A soldier should be doing as much DPS as possible so that the flanker can get a pick, the tank should be trying to push the front as much as possible (but obviously pushing directly onto point is usually suicide since you'll can't deny fire from multiple directions when you get in there), the support should be hanging in back and not dying. If you are a Reinhardt and you dash onto point for the sake of contesting, you will watch your team get melted behind you. If you are a D.Va and not putting up a defense matrix in front of your dps and support, again, your team will die. If you are a Soldier 76 and you aren't shooting when your team is pushing back, instead looking to just sneak onto point, your team will die; well, maybe they'll look at you for a second, kill you, then kill your team next.

You should be trying to stay alive as much as possible to execute your role on the team. Solo contesting point can be annoying to the enemy team and get attention for a moment, but is a fast track to dying.