Quote from Agtrigormortis»
But you can still get iron off zombies using mob spawners, albeit with a much lower efficiency because the iron ingot drops are not guaranteed per hit, they're a low probability. What would you say if this too were removed? then you would lose the only remaining renewable source of iron ingots.
If iron were to be made non renewable that can cause significant problems, especially with players who use legacy console world types which is still technically possible on Java edition with world borders.
I don't know about everybody else here, but I personally wouldn't want to play on a Minecraft world if I knew some time down the line resources were going to run out, as this would defeat the entire point of the infinite respawning mechanic on difficulties below hardcore, which is to remain on the same world with your friends no matter the length of time, for as long as you were alive and in enough good health to play, you could continue to do so on the same Minecraft world continuously earning new resources, encountering more landscape and building more structures.
Zombie ingot drops fall into the other end of the scale: They're too rare to be worth considering as a serious iron source. The only less feasible source is to buy iron gear from blacksmiths to smelt it into nuggets, and even that one at least can be automated, not to mention you can partially cut down on iron use by directly using said gear.
The only current reliable sources of renewable iron that can be used in some way a s amain source are iron farms (which are OP) and piglin bartering (Which is reasonably balanced, but pretty much requires automation).