Whilst I don't think denying is a massively complex mechanic, it does widen the gap between poor and good players.
This is why it was removed from LoL, the devs saw it as "anti-fun", whereby noobies could be stomped even easier by better players or premades.
So they removed it, and other mechanics deemed "anti-fun" like mana-burn. This makes the game more accessible to noobs, which tbf is needed. They are a business first, and if noobs get stomped constantly, they are likely to stop playing and never buy the new champ or get a legendary skin, etc.
That said, this is also why I play LoL. I'm not a massive fan of overly strategic games, haven't played an RTS since SupCom1, so the fast paced click-a-thon of LoL is more my thing.