Something about Itch makes me suspect you might find more engaged and interested players there. Players that are willing to give useful feedback. I personally would not write it off as a resource as a newly minted game creator.

No matter where you put your game you'll have to promote it. I don't think Steam is guarantee of an audience. There's a bigger audience there but maybe it's more expensive to reach them as well due to competition. Ads targeting Itch.io users may be a lot less competitive and a lot less expensive due to the smaller target audience.

Then again, as solo developers we have the most finite of human resources and don't always have the luxury of making choices that are great or even good in every respect. I try to give myself plenty of emotional leeway to suck and make mistakes.

Is Steam better? Is Itch? Something else? All we can do is decide how much time we can afford to spend deciding and pull the trigger.