Not that I can really talk since I just got the game, but of course people are only complaining because they don't have them. Just like you're not complaining because you have them. Darn, you need those stupid Infinity characters, that you have a concrete matter of fact method to unlock. Every other sticker in the game works in a manner that they give it to you before giving consumables.
The characters you desire are not stuck behind a paywall with a random number.
And to the person who gave the CS example - that's not a good example. CS:GO unlocks work nothing like Garden Warfare ones. And as I stated above, the Legendary stickers are the only ones that work in this way. And by that I mean that they for whatever reason aren't part of the 'guaranteed customization' slots of sticker packs.
The 'earned it' example isn't good either. I would assume most people commenting mean the 'deserved' definition of earned as opposed to the 'obtained' definition, as the 'obtained' part is rather implied by most comments.
Take Halo's Req Packs for example. There are different Raritys of Reqs, and the packs work almost exactly the same as the PVZ ones. The exception is that the Equipment slots are guaranteed to give everything from that pack until they stop. While some people may unlock higher ranked stuff first, there is a maximum amount you can spend to have everything.
The only caveat I'm willing to concede is that at least none of the packs are lying. None of them guarantee you'll get Legendaries. They should at least have some sort of function in place to increase your chances to earn a Legendary for every pack bought or something. A lot more games seem to do that now.
But in the above regard, yes, no one 'deserves' it. But it's a really greedy move to make when they have characters that are never guaranteed to unlock AND the opportunity to spend real world currency.
You can not fault people for wanting something that they've had to put way more work into that you and still have nothing to show for it. (Yes some things are easier for some people but we have quantifiable currency that shows more had to be done.)
But as I stated this is all coming from someone who hasn't played much. I tend to be pretty completionist when I play games and I'm guessing most of the people complaining are too. It just seems weird to have just a few things that are luck based from the pack when all other stickers are guaranteed after a maximum money input.