No competition will help the stock, but is likely to hurt innovation.
Sure it does.
Tesla would never have become so valuable if there was serious competition in the market for electric cars.
Competition often brings prices down.
If there was serious competitor to Facebook for example, it would have been more catastrophic for them to have that data breach couple months ago that leaked like 500 million peoples contact information, but because they're practically a monopoly, the stock didn't even flinch.
If there was 100 similar games like Cyberpunk, it would of course hurt the sales of Cyberpunk 2077 due to people having to choose which game to buy.
Heroes of the Storm was Blizzard MOBA which could be argued improved a lot on what MOBA games did wrong, creating less snowball, and having objective play with 5v5 fights. The reason why that game didn't turn out financial success was because of the competition. DotA, League of Legends, Smite, Battlerite, Infinite Crisis, Strife, Paragon, Arena of Valor...
If Blizzard had took note when the game was just WC3 mod and started seriously working on Heroes of the Storm, and release it same time with League of Legends, it would likely be most viewed game in Twitch today.