I guess what you could do would be to add a section in your description where you offer a dollar or two via [service X] for mails including insightful and/or constructive feedback.
They would have to trust you, but it would also give players who already like your game an opportunity to refuse getting paid for their input, making them more motivated to write something. Everybody likes feeling charitable - especially if they don’t actually have to spend money. ;)
The main downsides to that solution would be: Having to do the transactions manually and dealing with spammers. But the latter could happen in basically any scenario, as Dark Dimension already illustrated.