Arguments against RNG:

The current video game market do not like RNG much, Julian Gallop's remake of Chaos: The Battle of Wizards, one of the best RNG management strategy game in history, got bad reviews by players largely because of this.

For singleplayer, the player would usually reload battles lost by bad luck, but not the ones won by good luck. He ends up cheating in a sense even without save scumming.

For multiplayer, to get a fair outcome you may need multiple matches to approximate statistical average, which is several times more time consuming.

Calculation by a player in any complex game is already largely statistical even without RNG, have you seen how a advanced Go/Baduk/Weiqi AI, such as the ones beat the top players work?