When Richard Garfield, the inventor of Magic, was asked what he felt his biggest mistake was when making the game, he replied: Lands. I think it’s telling that every even moderately successful card game to come after has done something different when it comes to resources. Garfield himself said: “I didn’t like that Magic had about 40% boring resource cards in the deck.”
One could fix this. One could (just as an example) take a normal deck and separate it into two -one land and one nonland- and let the players pick which to draw from or mill from. This would make it so you always got the correct number of lands (if not correct colors). But, I am sure people will comment explaining why they don’t like this idea. (‘Oh no, Mill would become more powerful!’)
I think the new mulligan rule is a step in the right direction. When I first started playing this game in 1994, many people had a house rule saying you could rearrange the top three cards after mulliganing. In causal play people have all kinds of ways to make lands less of an issue, and people have been posting ideas how to ‘fix’ the problem since the internet was a thing (as I just did above). Regardless, Wizards has always maintained they like the fact that occasionally someone gets screwed by lands because it adds another layer of luck to the game. But, I think after a few lackluster protour feature games, they decided something needed to be done.
Having a person lose the last game of seven just because they had to mulligan to four isn’t fun for anyone to watch.