So lets assume you use classic and make a great game people want to play and even pay for...(hope you do)
To start with, It would take at least a few years work to come up with a Mario sized platformer, after years of effort and time you have your completed game in Exe format...
Even if you initially started this for fun and had no intention of selling it, by this time you will consider it has value ??
It will only ever run on a desktop PC, and then someone will ask if there is a version for android or maybe Mac...I guarantee at that point you will wish you had used C2...
As you say, most large projects on Classic have been either abandoned or ported to a different engine, this is telling you to use C2...