First and foremost disadvantage is all the ideas you have will be sitting in your brain itself, as you have not given clarity to them to flow out and have also not tested are they just your thoughts or it can be implemented.
You cannot raise funds for your project and take them to next levels, they just remain as ideas and when one fine day you see the same idea being done by others and tasting success you feel I should have done that.
You are stuck as you don’t have road map that means you don’t have clarity to put down what is that needs to be done first and what next. It clearly shows you are not good at planning or you are not in a position to document things.
You will not have clarity as to how much funding is needed and how to run the business what type of business model, what will be revenues from it, you will also have no clarity on is your idea actionable, implementation and executable
When you talk about your project to other people there reaction will be ok how are you going to do this for which you will not have answer as you have no clarity on how you want to take your project to next levels.