"We chat" is just to combination of multiple apps. There are many apps with similar concepts like messenger apps. You hardly find any uniqueness in Skype, WhatsApp, Viber and signal etc. but all are successful and have billions of users. They all trying to solve same problem with similar solutions. The only difference you find is UI design and some minor things. Similarly, Udemy, LinkedIn learning, Lynda and Edx offers almost same services. Do we need to find problem or can we solve same problem which is being resolved by competitors?
Yes, you should be solving a problem that affects millions of people. Nice to have is of little interest for investors...unless is a moonshot.
If affects billions of people, and in different regions, there is a lot of market share to split amongst several players, which is the case of messaging apps, email providers, etc.