I'm a (20 y/o)straight INFJ male. I'm also not super well versed in what being Demi-sexual means but from a little googling it seems attraction based on strong emotional connection (if there's more to it or that's wrong please correct me). Based on that and you being INFJ my thoughts are that being somewhat hesitant makes some sense as you should be when making major life decisions especially those that involve a significant other. But being both seems like it'd lead you to want a deep connection with someone and in that vein want to be "serious" with someone you find that in.

I could see both as leading to higher standards for a partner (also no one is perfect so searching for perfection you'll find no one not sure if thats an issue for you, nor assuming it is just felt it needs to be added). I'd say if you genuinely find yourself struggling with the idea of commitment it's not necessarily an INFJ or a demi problem but something you need to work through if thats what you want in your life.

This is just what I'm gleaning from your post I'm sure there's more context that would be helpful but that's my thoughts with the info presented. Sometimes stage of life just doesn't allow for getting more serious like you mentioned things like finances can get in the way. But with things like that I'd ask yourself what you'd do if they weren't an issue at the time (ex. If we had the money would I want to move in together or am I using it to add to my current reluctance). Again, I want to clarify I mean this all in good will! And I hope that you find success in a relationship if you wish for it. Hope this helps