How to actually find your competitors
Search the obvious terms in Google, then search how a frustrated user would phrase it. Check Product Hunt and the App Store, look at G2 and Capterra for software in your category, and search Reddit and forums for "alternative to" and "vs" threads. Within an hour you will have a list. If you find nobody at all, be careful: it usually means no market, not a blue ocean.
Competition is a good sign, not a stop sign
Finding competitors means someone has already validated that people pay to solve this problem. That is far better than an empty market you have to educate from scratch. The companies you admire almost all launched into crowded spaces. The question shifts from "is it taken" to "is there room," and the answer to that lives in how unhappy the existing customers are.
Mine competitor reviews for the gap
Read the one and two star reviews of every competitor you found. Each angry review is a free list of what people hate and still pay for. Look for the same complaint repeating: too expensive, too complicated, missing one feature, terrible support, built for a different size of company. A repeated, specific gripe is your opening, and it is far more reliable than guessing at a feature nobody asked for.
Win a slice before you win the market
You rarely beat an incumbent head on. You win by being clearly better for one specific group they serve badly. Pick the narrowest version of the buyer whose complaint you can answer best, and own that slice first. "Taken" by a generalist usually means wide open for a specialist, so define who you are unmistakably the best choice for before you worry about the rest.