That being said, as OP says, an upvote != a customer.
But it's still valuable for marketing. Here's how I think about it:
1. their mailing list which goes out to .. 100s of thousands at the least. Your ICP may not use PH every day but if they work in startups, they are likely to have an account.
2. people google your product and find the product hunt listing. It's good SEO. PH ads actually have done well in getting ICP customers for us.
3. [most important] product hunt is an alternative to a press release. the traditional way to launch something is to pick a day, get press, then amplify the heck out of it across all channels. getting press as a small startup is hard and often outside your control. You can use Product Hunt as your "press release", then tell everyone about your launch-investors, friends, customers, ask them to share on LI/Twitter etc. You get people talking about it. This is where most of the value lives.
what OP is describing in their post is sales which is obviously a more direct way to hit your ICP. but marketing also has its place. especially in a world where your ICP is getting bombarded by sales reps, automated SDRs, etc