I'm pretty sure you've found yourself asking this question to yourself "Should I go after this niche"?
That is because Keyword research is the most important process when it comes to the success of your SEO project.
Sometimes you can find niches where KD (Ahrefs Keyword Difficulty) is less than 5 but all the domains that are
I used to wonder the same thing. Then I launched a project where most of the keywords were like you mentioned i.e. super-low KD but high average DRs and what I found was that at that point relevancy matters a lot.
Study the competition and see how their content fare's for the particular query. If you see an opportunity to create content that is more on-point, relevant, does a better job of satisfying user intent, then the high DR domains should not necessarily be seen as formidable competition.
My year old site was/is comfortably beating the high DR domains. Basically, the aim is to create content to achieve that "long" click. At least that's been my observation in the past year.
A SERP pattern with varying DRs is an obvious giveaway that there is an opportunity to rank. But my comment applies even to ones where the top 10 are all high DR, but KD being low which means the sites ranking doesn't have backlinks to those pages.
The nitty-gritty of this post
For example, if we take this keyword into consideration: trail camera review
You can zoom in the photo at - https://imgur.com/k5d8L88
We can see that sites have much less authority like trailcampro.com are ranking better than high authority sites like gearhungry.com
That is because trailcampro is a more relevant website to that particular query than the other authority website.
The first website has around 800 posts for that query, while the other authority site has only 3 posts for that query. This simply tells us the reason why some low authority sites can dominate a small niche and beat massive sites.
site:trailcampro.com intitle:trail cameras