Great blog traffic but other important pages are getting left behind - are backlinks THE answer?

Hi, i need your help :) so our website is split into 3 different sections:

- blog (we're getting great organic traffic with it, lots of useful long posts...)

- nonprofit collabs (backlinks from other respectful companies -> we're ranking with it pretty high)

- the actual service we make money wiith (great keywords, optimized, structured data, etc. but never shows up in SERP)

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How is this possible? Do I need to find a way to get some valuable backlinks to that specific page? I already link to it on almost every blog post - is that not enough? It's almost impossible to optimize it more with copy/code...

Some blog posts might compete with this page as well even though it's not that relevant. Do think it's worth trying to remove some of those posts?

I need this page to be the biggest - are backlinks the only answer for us at the moment? Or is there any other aspect of SEO ranking that I may have overlooked? Thanks!