Hey Mark! 
Thank you for sharing your feedback with us in the Community–I hear you. Importing via Excel or CSV can be frustrating when users are limited to syncing their data to a Text, Status, Date, Numbers, or Phone Column. I see that you have already dedicated time to build out all of your columns prior to the import as well.
I wish I could give you an immediate solution here! This is a common pain point for many new users. I encourage you to upvote this ongoing feature request here: Excel Import in Board - Greater column support.
With more votes, our Product team can continue to prioritize this feature on the Product Roadmap.