Our team has recently found an open-source sales management CRM tool, Meow https://www.sales-funnel.app/, which they are happy with. Licensed under AGPL, it might be worth a look for startups.

I guess there are definite reasons why open-source isn't as successful in the CRM space. Buyers are mostly not developers and the requirements for a CRM are often very diverse. I agree with earlier comments, Salesforce is not just a CRM.