What are those links you are talking about? I've had web2.0 blogs that have been around for more than 5 years with multiple contents in them and still not indexed to this day.
There are many factors and reasons why your backlinks are not indexed, and there are several ways to index your backlinks.
1: Your Backlinks are Not Worthy of Indexing
2: Your Content is Very Thin and Plagiarised
3: You Are Creating Backlinks from Sites With No-Index Tag
4: Share Your Links on Social Media to Improve The Odds of Getting Indexed
5: Build Relevance Links on Authority Sites
6: Web 2.0s
7: Submit Your Sitemap to GSC