I've Ticked Higher DA, Backlinks but still not ranking? Advise plz

Hi community,

I've been on SEO for some time, and for the last year I have been honestly rusty, as my responsibilities increased I don't have as much time as I used to before and I need your suggestions with my site.

My site has a higher DA then my competitor including more backlinks, but I feel that Google has penalised my overall site since we changed the site last year from 1 theme to another and it hasn't ranked as high. Arguably, this could because some posts were missing.

For example, 1 content was not available for 11 months then once I pulled out of the old database it skyrocketed back to position 2.

What are the implications/causes as I can only think the lost 4-5 posts have been deletet, aside from that my site was ranking between position 1-4 and need to get it back there..

Thanks in advance!