The Reality Behind Dota and League's Downfall

This person makes a lot of good points, including

• players nowadays have a lot of others options to have fun, MOBA are not the only free-to-play games anymore
• entry cost is very high for new players to get to MOBAs, preventing playerbase renewal
• original players of the game are now aging, and don't have time for 30-60 minutes games
• other modern games are more accessible and fun (e.g. Deadlock)