Two different questions here really.
Evergreen but brutal to rank
Health, personal finance, insurance, loans, crypto, weight loss.
These are YMYL. Google wants a real named author with credentials
before it ranks you, and the sites already there have link profiles built over ten years. Steady demand, but you are not getting in with a new domain and no authority.
Evergreen and actually enterable
Hobbies with expensive gear. Specific software and tools. Pet sub niches like one breed or one condition. B2B topics that are too narrow for big publishers. Home DIY on specific jobs rather than general improvement.
Demand is smaller but the competition has weak links and thin content. That is where a new site can actually win.
Same rule for both. Pull up the top 10 for your main keyword and look at their backlink profiles first. If everyone on page one has thousands of referring domains, pick something else.