Competitors rank fine without much/any external links to the landingpage, seemingly thriving on the domains authority and internal linkbuilding to their dedicated landingpages, but ours do not
Yours "do not" what?...
- Don't rank?
- Don't have internal navigation?
- Or that you have good internal links as well as whatever else your competitors have?
How long has your page and domain been up? How old are your inbound links? How old and established are your competitors' sites?
Yes, it's very important to look at your competitors... but look at their sites sympathetically.
Instead of looking at their negatives, comparing them via some third party number that doesn't necessarily relate at all to how Google sees your site... you should strain really hard and look at any good aspects of their sites that might be causing them to rank.
Compare very critically. See how you measure up to them.
Look, eg, at...
- unique, useful information about what you are selling
- unique articles that relate to the experience of using what you are selling
- do you have a unique value propositon? Why should someone use you over them?
- quality of information
- quality of writing
- site structure
- quality of their backlinks. Google values freely-given editorial links from sites that themselves have freely given editorial backlinks.
- longevity
- technical metrics
- social presence
- advertising and buzz
- UX
- etc
- etc... at least several hundred etcs
Do your competitors have a known brand? Do you have a known brand? How have you gotten your backlinks? Etc etc etc.
...our domain having slightly less authority (measured by DR on Ahrefs and similar factors).
This means that if Ahrefs had a search engine and ranked sites by comparing only your DR's authority with your competitors' DR authority, you would rank "slightly less" well than your competitors do....
We are here, though, talking about Google, not about that imaginary search engine that Ahrefs doesn't have.