It's immoral on several levels, but especially on two points:
Firstly, most of them announce "release dates" for a product that is not in release status. Just check Steam, check release date for say.. Vagrus, the Riven Realm. July 22nd. That is not the release date, that is the Early Access launch, which give you a flawed, incomplete product under development, god knows if it'll ever be complete at all. False advertisement is a crime where I live.
Second, testing early stages of a product to get feedback is something companies in all sectors have done for decades. Only you get paid for doing it, since it's a flawed, untested, or incomplete product, and that's the key factor. Only the gaming industry can scam you this way and you'll have people defending it.
We could speak about how greedy developers want to cash in even before the game is complete, how stuff that would have belonged to the main game now gets branched off as DLC to get more money off their Early Access supporters since they're running out, and they have already paid for the game.. might as well milk them further. That and a thosand other shady practices of something that as I said, only the gaming industry gets away with. I can't imagine a pharmaceutic corp saying "Hey, we got this new untested, unfinished drug, that in theory, will make your senses sharper if you have 3 doses a day. Wanna pay me what would be its final release price with a 20% discount and on top of that test it for me, tell me its side effects, and provide me with feedback to make it better for all the people that won't risk dying to it when it's finalised?"
It's just absurd.
"But nobody forces you to buy early Access!" Yes, and nobody forces fathers to enter the gambling houses and ruin their families. The fact that something isn't forceful does not make it morally acceptable. And of course, nobody is going to ruin their family for paying 20$ for an early access game, but there are immoral practices behind it, the same way as there are immoral practices behind selling lootboxes or XP boosts in single player games, and nobody forces you to buy them. It just shouldn't be a thing because it damages our gaming culture as a whole.