I think the over the fold area is very clear, except the "Tired of endless software subscriptions?" thing looks way too much like a button.
Searching doesn't start if I enter a search term and press Enter key. In fact, the entire search feature seems broken. If I enter a search term and try to search for something, the search input field just gets emptied and nothing else happens. This is completely broken.
I don't like how the email subscription thing is the first thing visible on the main app listing page (e.g. https://payonceapps.com/explore/platform-windows). It's very annoying and obtrusive. Also, the website has literally no privacy policy information, collecting emails from people like this is not user friendly, and could even be illegal depending where you are based at.
Since price is one of your main selling points here, I would prefer to see the price information at the main app listing UI instead of having to click to open the app's individual page.
It's very confusing why the tag boxes on the left show the mouse handpoint cursor to indicate that they are clickable, but on the main app listing UI the exactly same looking tag boxes don't do that. And when I click them, there is a substantial delay when nothing is happening, making me think the website is glitching again (just like how the search is not working at all).
Overall, I really like this idea, and I hope you could fix the mentioned issues and this would be very nice!