Yes and no. The previous answers above are important and necessary.
☑️ Yes, you need an idea that pops!
☑️ Yes, you need an outstanding vision and in-depth knowledge of your market
☑️ Yes, you need to have a well-planned goal.
However, I would just like to point out that it becomes a lot easier for everybody, including you, if you've already have a "Beta" app up and running. This way, you can already listen to what the market is telling you and know what to "fix."
Yes, I have no contentions about the power of funding and a well-oiled operation, but finding that base line on what this app can really be based on how the market has reacted would be a more challenging, but also a more rewarding way to go.
To put it simply, you can create a simple code for a "Super Calendar/Calculator App For Business" while it's still in beta. During the Beta stage, you get feedback from the users that this and that is what they would really like to have. Now, after that phase, you improve and you adjust.
Let's just say, you're ready with Version 1 with all of the positive feedback from your existing userbase. That's, I believe, is the time to reach out to investors since you already have momentum going.
Hope this helps!
If you need further assistance, let me know!