I would like to start off by saying I firmly agree that some source of iron should be added, whether it be introduced by piglins, golems, zombies, or other methods. I think with recent updates there has been an increasing need for iron, from lanterns, to chains, to blast furnaces, to smithing tables. I think "because we've never had iron farming before" is a bad mindset because clearly the game has changed, and something as it was in 1.4 is considerably different 12 full releases later. Times change, we probably should too.
I'd like to add that the next point of this post is going to be solely from my experience playing Zurvival, and what I have experienced.
On Zz, I have mined a little over 16,000 iron ore. As far as I am aware i have never placed iron ore and mined it again, maybe once or twice but never enough to significantly skew that stat as I would have silk touching and later fortuning diamond ore. In my time I have never really considered myself short on iron, I always had enough for anvils, or hoppers, or pistons. As of late, however, I have been attempting to upgrade some mini-bases with full beacon pyramids, and I realized just how outmatched I was in terms of resources. A full beacon pyramid requires two stacks plus 36 iron blocks, and that isn't even considering the fact you need even more to make every effect on multiple beacons possible. I think realistically, it would be invaluable to be able to farm iron on a scale that allows me to upgrade full beacon pyramids, but much to Mell's point I think getting it handed to me on a silver platter would greatly diminish how impressive it looks. I think right now we're lacking a fundamental piece of the endgame puzzle in iron acquisition, and even though zombies drop iron ingots, the rate they drop it is so astronomically low that it makes it just plain stupid when you can go caving or beacon mine a large chunk of the underground to acquire iron at a considerably faster rate, at the cost of a few pickaxes and ender ender trips. The iron I've acquired has all been through caving, bar maybe a couple hundred which was acquired through branch mining methods. To this day I still enjoy caving, I enjoy the fact a creeper might catch me off guard and knock me into a bunch of skeletons. I'm not sure if that rush will ever go away, I just like to find ores. It's how I play.
The next part of this post refers to my experience on LVS, and how I believe it relates to Zz.
On LVS, I farm, and farm, and farm, and farm, and farm. I gather items for the sake of gathering items. I sell them to the community, but much of the time I have an over abundance of everything and I like the fact I can honestly tell myself I can do anything if I put my mind to it, just because I have the items to do it. Recently I created a 24-cell iron farm that makes so much iron that I can probably use iron blocks as someone else might use stone blocks and I probably wouldn't even make a dent in my supply. I think that's awesome, that it's possible to do that in vanilla minecraft, but sometimes I think about how much effort it took to create that farm and it saddens me that such little effort can produce such a ridiculous amount of iron. I think this is why I like LVS and Zz, because they are so different to me. This isn't to say Zz shouldn't be for the farmers, and that LVS shouldn't be for the explorers. I just think Zz and LVS are so different now, that we can't say "it's like this in vanilla minecraft" when frankly, Zz isn't vanilla minecraft. On Zz we have region posts, homes, claims. Simply adding something in because it's like that in vanilla just doesn't sit right with me.
So, what do we do about iron on Zz?
I think simply switching on iron drops is a bad course of action. I also think turning iron nuggets on with bartering would be very helpful, and to that end I think we should do it. That being said, to Tezcatlip's point, it just wouldn't produce the amount of iron that certain endgame tasks necessitate. How do we fix it? I think the solution is to turn on iron golem drops, but either change the item they drop to iron nuggets, or change the drop rate of iron ingots from golems down to one ingot per golem, rather than 3-5 as it is in vanilla. I also think that it should be somehow tweaked so giant iron farms cannot spawn multiple golems at once, say one can only spawn at a time within the render distance, and until the newly spawned golem dies, no more would spawn. That would ensure that your rates would only be as fast as your golem can die.
I don't really know where we'll be going forward, I just think that it's wrong to not have iron not more easily attainable when the direction the game is headed seems to be reliant on iron in some form.