This depend a lot on the app. If you're selling an oil and gas company on something that will better forecast their well production over the next decade, no one cares.
The big things to consider about your product are
Will you get another chance to pitch these people? If your potential customer are accountants you can pitch with a more minimum mvp. And if they don't like it just make it nicer. If you are leveraging your connections to sell to a fortune 500 company than you need make sure it's more polished.
Are the people who are going to be buying your product also going to be using it?
For instance if VP's will be buying it for their operators they will care less about look for screens they won't use.
Are your selling to organizations/business or consumers?
Organizations will care less about look and feel.
How many competitors do you have?
If you have a bunch of competitors than you need to distinguish yourself more with a great look and feel. If you don't have any it's not as big of a deal.
How much value are you adding to your end users
If you're adding a lot of value then look and feel is less important.
How are you distinguishing yourself from the competition based on look&feel, capabilities, or price?
If it's capabilities or price it's not as important.(They do x, and we do x but for $50/month versus
In the end it's all about what's your sales pitch and branding to the end user.
Why are they using your product versus using a competitor or not using your product at all? How much will look and feel influence are part of this decision?