Received 6 links from OP
Site metrics: Each site have at least 20+ DA. They also have 5-10% moz spam score.
Article Quality: Simply put, it is bad. No natural flow. Just a bunch of loosely related sentences stringed together with my link inserted in the first paragraph.
Backlink profile: Surprisingly amazing link profile for all the sites. One even got links from popular news sites.
Footprints: All the sites have the wordpress sample page still visible with the default wordpress favicon. the site themes look identical too (leaving obviously huge footprints in my opinion).
Suggestions: Improve the article quality. They are not suitable for t1 links at all. Even AI written articles will do as long as it's readable.
Also add logo, favicons and refurbish the themes.
Honest Review: You could improve the service by a whole lot. I know you're offering the service for very cheap prices but still quality of service matters in my opinion. Especially given the backlink profile of your sites a little emphasis to article and site theme quality can make your service an S tier one.