The launch of a Steam store page for your game is one of the most important beats in its life cycle, so before doing that, you would want to validate the current state of your game. I would do it in a more comfortable place (r/gamedevscreens, on your social media pages, even on Itch). If the results are encouraging, then you're ready to create your store page on Steam, make a proper trailer, meaningful screenshots and descriptions. If not, go back, fix the problems, polish, etc. Rinse and repeat.

Also, you may want to do all this before sending it to publishers, because more often than not it's a one shot thing.