No. Coinmarketcap.com is not the only platform where you can monitor prices of all cryptocurrencies.
We have many others that I will list here.
There is coincodex.com
https://www.coingecko.com out of a number of others.
We also have applications that you can download on mobile that will do the work.
However, most people use coinmarketcap.com because of its simplicity and fast loading pages. It is also well rank on Alexa