"And the game has to be fun for beginners too"
I don't think that true.
If you want your game to be a big seller and reach a ton of people? Yes of course. For a quality competitive game? Not necessarily.
For exemple I got total shitwrecked when I first started playing fighting games, especially SF4. But I bunkered down and once I was familiar with it the game opened up and the competitive fun I have is unrivaled. It's very hard to not step on the competitiveness quality of a game when trying to make it accessible. For example I'm not sure I would have the same quality of fun with say Divekick, which is way more accessible. Divekick will be fun for 20ish hours, in SF4 I have 350hours clocked in and I still learn new stuff and improve my game each match and it's still super exciting.
I have the same exact story when I started Magic The Gathering and Hearthstone, Dota with League of Legends (I still learn new stuff in Dota 2 with over a thousand hours in it and the game is still amazeballs.), CSGO with CoD.