Advanced keyword planner

Idea: Advanced keyword planner

That helps you to choose popular keywords that in use by not so many competitors; proposes alternative keywords; shows who those people (age, gender, preferences) who search the keywords.

There is a Google Keyword planner, which is free and provides good numbers on what's going on in search. The only issue you should know the keywords you want to research and you should then research the websites' domain authority scores that appear on the first page on Google.

Of course, there are Ahrefs-like solutions, but they won't suggest you a niche, keywords that are not competitive at the moment, or steadily grow and will be competitive in ~2 years.