The main game is just impossible to catch up nowadays if you want to have competitive decks and not spend money.
However, I love Battlegrounds and buying the stupid season pass doesn't do much 4 me (4 hero picks instead of 2 and cosmetics that I don't care about).
As someone who's been playing since season 1, I can't imagine starting the game now and learning all the champions, there's so much shit. Also low levels are filled with toxic smurfs which just ruins the experience. So yeah, I'd say LoL is a dead game for new players.