No. The reason the intermittent game modes are high quality is because they are NOT permanent. It takes a lot of resources to develop game modes like this. Every single game mode as definitive champions that are stronger. A meta comes up and then that needs balancing.

ARAM is a good example of this, the only reason it still works is because champ select is random, and even then you still have ARAM only accounts with the intention of always getting a strong champion.

Which brings us to the second issue. Maintaining a permanent game mode that doesn't have the random champ select requires a lot of resources to maintain.

If you doubt that just look at Dominion. Dominion was a good game mode, that lacked support. Support that Riot could not adequately provide when it was first developed Dominion without sacrificing investment into SR. People give Riot a lot of flak for their neglect of Dominion, but if they invested into it and it flopped, and the quality of SR declined rather than being the most popular game in the world LoL may have simply fallen apart and been overtaken by the multitude of competitors that were presenting themselves.

Dominion is effectively a dead game mode because it lacks development. Development that Riot probably could invest in now, but to do so would mean no longer investing in developing the fun temporary game modes.

This brings us to the final point. If you really like something in one of the temporary game modes, then be vocal about that. The temporary game modes are a testing ground for new ideas that could potential make it into the actual game in the future. They are also good for getting large scale data on champion balance and small changes to the game that could make them really strong, or certain items really strong.

I personally would rather see higher quality development of temporary game modes. Rather than poorly supported permanent game modes. Because poor support is simply going to kill the game mode and plus it simply is not worth the risk for Riot to develop a permanent game mode that is effectively in direct competition with its own game.