Your friends are stupid. Tetris is Tetris no matter how you look at it. You might as well be saying Super Mario 64 and beyond isn't Super Mario at all.
The inclusion of hard drop and ghosting made the game more exciting and faster making for intense matches. However, I don't like the modes other than marathon.
It's more like only 1 or 2 friends that's stupid. Regardless, I posted this because I wanted to see a wider variety of opinion, not to see a bunch of people insulting my friends.
Retro is funnest in solo. Modern is not because it is too easy with hold piece, infinite rotation, etc. These don't affect Modern in multiplayer because if you sit there and spin the piece for longer than 1 second, you will lose.
You know, infinite rotation's only a thing in Tetris Worlds and Tetris DS. The ARIKA Tetris games, as well as the more recent Tetris games, handle rotation much differently (as in, they allow rotation after landing in order to allow trick placement such as T-spins, but has a short timer to prevent infinite spinning).