I propose a reasonably simple addition to game rules of the draw step that could help to smooth game variance while still maintaining the integrity of the game in most cases:
At the beginning of the draw step, the active player names "land" or "nonland". Then they draw their first draw step card, and may choose to reveal it. If it doesn't match the named card type, then they exile the card and put the top card of their library into their hand.
One could also imagine variations that add a cost (such as 1 life) and/or repeat if the next card also doesn't match. (The repeating one is more risky from a combo exploitation perspective).
Overall, this should make many more games much more fair and fun, while still preserving the RNG and hidden-information feel of a card game, and also largely without invalidating existing game mechanics.
I haven't done detailed calculations to quantify how effective this rule would be to reduce "un-fun" variance, but an extra chance each turn should have a significant effect.