I look at a fair number of link profiles, and they nearly always fail in the same places. None of them need an agency to fix. They just need someone to notice them.
1. Everything points at the front page
When 90 percent of your links point at the front page, it does not look like something anyone did voluntarily. People link to the page that answered their question, and that is rarely the front page. Send the next links to subpages, articles and categories, even though it feels wrong because the front page is the one that matters to you.
2. The same anchor text every time
Exact match on one keyword works, right up until it does not. It is the most readable pattern there is. Mix in your brand name, use full sentences, use the raw URL. Your link profile should look random, because random is what real links look like.
3. Every link comes from the same kind of place
Nothing but directories is just as transparent as nothing but blogs or nothing but comments. It is not the number that gives you away, it is the sameness. If one type is clearly overweighted, you know where to start.
4. You do not notice when links disappear
Sites close, pages get deleted, editors tidy up. If you have a link from a page that turned into a 404, it is gone, and nobody tells you. It is worth checking your own links now and then, because reviving a link that used to be there is far cheaper than building a new one.
5. You build too fast at the start
This is the one that does the most damage, because it feels like progress. Going from 2 links a month to 60 in three weeks looks like exactly what it is. Turn the volume up slowly, and let the curve look like something that grew.
The order matters
If you only fix one of these first, make it number two. Anchor text is the only item on the list that can give you a real problem rather than just wasted effort. The rest you can work through as you go.