"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?
Hi. Theoretically you can do anything you want. However practically it may be not be adequately profitable or even profitable.
If it is high growth market and you are relatively early then potentially you can do the same thing that others are doing but you have to monetize sooner. As market matures you will need uniqueness to continue to be as or more profitable than your competitors. Else likely you will operate at low margins or even negative which will make you exit the business.
All examples given by you are relatively mature areas with number of competitors, many with unique offering, and many with bigger names. If you go with a similar offering then your cost of entry will be high. This will hurt profitability. There are smarter ways to do this.
Hope this helps. Let me know when we need to talk. Bye.