why is picking 1 cantrip over another important but picking 1 background feature over another not?
like I can make food at will or I can move 5lbs of weight with my mind at will, or I can make little balls of light at will
I can scavenge for food always, or I can have 3 servants, or I can know some secrete of the world...
both are opportunity cost
going down this train of thought can lead to no feats, no skills, no tool prof, no classes... just 6 stats and everything is a stat check
A lot of the times, when I discuss things about 5e I don't particularly like, say for example, how using a Cure Wounds in combat doesn't feel great, or how I wish there were better options for a more 4e-ish Fighter (say, a Battlemaster who can perform maneuvers every turn, but isn't broken based on bonus damage dice), someone usually comes along to point out that you can change the game to allow for that.
If you want this or that element to be different, you're allowed to change it, that's the beauty of 5e and why it's the most popular version of D&D that has ever existed.*
*Some hyperbole here, but not really that much.
But when I flip that point around and say "well then, if something exists in the game that you don't like, you can also just get rid of it", people seem confused. So what if WotC decides Feats are core in the future?
You still don't have to use them, and even if WotC claims they are assumed in the expectations of the game, so what if the game is harder? I hear a lot of people claim 5e is easy mode anyways.
Or let's look at one of the big "optional" parts of the game. Magic Items. We're told they are optional, but many people assume that magic weapons will appear at some point. Heck, there's a sidebar in Xanathar's discussing how the game changes if magic weapons aren't around, and how certain class features and spells become much more important to make up for their non-existence...
If I can be told that "the game works fine because rule zero exists" then that should be universally true.