Need help with the first B2B sale

Working on a B2B based SaaS tool for improving productivity among teams!

We built a very crude MVP and before we put in an extra effort to create UI and launch more features, I am trying to reach out to founders who I think could be potential clients for a quick 15-20 min call, to explain to them the product and take feedback. (Not to push for a sale in the first call itself, I want their unfiltered advice).

Am utilizing multiple mentoring platforms to be able to reach out to founders/ex-entrepreneurs in general but the TAT seems longer.

Any Advice on the above would be greatly appreciated, Happy to provide more context if needed!