Didn't someone earlier in this thread argue having two of X in the party makes X not rare even if X is super rare in the campaign world?
By that same logic, two pandas in a zoo makes them common? So that they are no longer an endangered specie?
So OK EVERYONE! ZOO "XYZ" HAS TWO PANDAS! WE NO LONGER NEED TO PROTECT THEM FROM EXTINCTION!
That logic is completely irrational. It was not thought through.
I'm also welcome to lay out why an argument that a particular design decision is inherenlty unfair has legs. There's a strong argument that gating poerwful character types with random rolls is inherently unfair due to the randomness involved. Randomness in play has the chance to even out because a character can make thousands of rolls in its lifespan. But rollng a paldin depends on only a single roll, making randomnes hugely more relevant to it.
You may, lay out your argument. But it does not make it true one iota.
Yep, you had to be very lucky to roll a paladin.
People can argue that paladins were supposed to be rare as a philosophy. I don't think that's accurate, or at least incomplete. Paladins were supposed to be rare because they were simply more powerful. They had abilities that made them simply better than fighters, because they were fighters with a bunch of extra abilities. There's a good argument that this is inherently unfair, because not only does the character get the benefit that high abilities scores normaly provide - already an advantage provided by randomnes - they also get access to a class with flat-out better stuff.
And I think exactly the contrary. It was exactly this reason that made paladin so desired. But since they were rare, most people were happy when they had one in their group.
Now. Not all paladin were parangon of strength, constitution and wisdom. In fact, many barely made it with the minimum stats. And before the UA, they would not get to increase their stats (that was completely BS when we saw that...).
Now, when you gate a class in such a way, you know that a group that has a paladin in it will have it a bit easier than a group without. Again, this is two philosophy at odds that we see here.
Make do with what you have or do whatever you want?
1st philosophy will have someway to reward good rolls with prerequisites and powerful classes.
2nd philosophy will try to push class and game balance instead.
1st philosophy will have a lot of variations in the actual play and will force players to work a bit more creatively to overcome dangers. Here the swinginess is what people are after. A high risk game where the odds are against the players almost all the time. It is exactly those odds that bring players to these games. The uncertainty of the results is what is exciting and enticing to play these systems.
2nd philosophy will see no or few variations, encouraging both cooperation and indiviualism in play. The more balance the game, the more the play becomes individual (even in groups) because you do not necessarily need the other to succeed. The "balance" of the game makes it that even encounters are assumed to be balanced and requires players to make major mistakes to die. Here, since the odds are equal or slightly in favour of the players, the story usually prime over the randomness. In the previous system, the story organically emerge from the die rolls and interactions between players with their environment. In the 2nd the story comes from the interaction between players with their environment since the randomness of the game has been eliminated.
Both systems have merit. Fortunately, 5ed can be made a bit more like 1ed by tweaking it a bit. (This is what we did).
The fact that you could choose not to play this game doesn't make the unfairness disappear. It just means some players accept it, if only because they didn't have any other options.
You always have an other option. That is not to play. If the rules are so abhorrent to you that you play reluctantly, my advice is do not play at all. Find another group. Or become a DM and make your own group that will like your style.