It's not about exp gain, it's about the autoloot being paygated. Not only do you need pets to avoid having to R every single loot pile, you need lots of them (from what I've heard) to tier them up, as at high levels even multiple pets typically get outpaced by the speed at which you clear mobs, leaving loot bags to decay (albeit to a much lesser degree than if you were trying to manually loot them). That's absolutely fucked, real P2W shit. Autoloot is a QoL standard, especially if you have fairly rapid loot decay.
I agree with you in principle. Paying for basic QoL stuff is a strong turn-off in games.
However, I don't feel like it is an entirely applicable complaint in this particular case. I've been playing BDO for about a year now, and currently have 5 pets; 1 of them I bought with the currency I got with my initial purchase of the game, the other 4 were given out free during events. I only keep 3 pets out at once; 2 would probably be plenty, but I overkill just because I can. I have not bothered to tier-up any of my pets, that is entirely unnecessary.
So yeah...the pet-looting system is entirely manageable without sinking tons of money into it.
Regarding other people's comments about the upgrading system, again I can sympathize, but BDO is not nearly as bad as many other Korean MMO's. First of all, weapons and armor never break on upgrade-failure; mid-level failures result in some durability loss, necessitating more frequent repairs or a modest fee(in-game currency, not real money) to restore the lost durability. At higher upgrade levels a failure may result in downgrading one level, but upgrades at that tier are entirely excessive to what you actually need to kill monsters quickly.
Also, there is a transparent 'failstack' system, meaning that when you fail you see a visible counter go up which increases your chances of success on further upgrade attempts. This system can be exploited by deliberately failing upgrades on cheap items until you have a high failstack count to use on your more expensive items, thus making the RNG quite manageable.
And if you don't want to mess with all that, you can easily save up a bit more coin and just buy pre-upgraded items from the marketplace. Items that other people upgraded usually only cost 20-30% more than if you upgraded them yourself.