This effect replaces your would-be card draw and returns that fetch land or cycled Indatha Triome to your hand, and as a drawback you mill two cards
Here is a quick recap of your standard turn structure
Once Melira's replacement effect has been applied in a turn, additional events that would put poison counters on a player don't happen, regardless of any other replacement effects involved
Obviously replacing some of the most effective draw spells in Magic isn't easy, but with a little effort you can find cards that will mimic those abilities and even sometimes turn out to be better
Guildgates, Shock lands, and also a new Mythic Rare land
Hour of Promise can help you to get a couple of lands directly to the battlefield, which can be great for landfall triggers