I've not ever played one, so I guess I'm your target audience. I read the whole thread. Im really not convinced to buy it. You clearly care so I'll tell you why you failed to convince me.
1. You don't really explain the combat. Is it a high point or just there? Is there variety? Bosses are just bullet sponges (fist sponges)? How is that fun?
2. So the only thing I know about the story is that it's got overly long cutscenes and it will be tough to remember characters names. Give better examples of why this story is interesting. I can watch 1000 crime procedurals on TV. Why should I watch this instead?
3. Show, don't say. Don't tell me it's good. Tell me why it's good. I don't know you. I don't trust you at your word for something like this.
4. Cut out like half of your words. You don't need them and this is too long. Literally half.
5. You need to address how going 0, 1, 5, 6 is going to be remotely ok.
6. The history of Yakuza does not matter.
I don't mean to be harsh. You clearly care about this, so I'm just giving feedback you can hopefully take and use to convince me and others this is worth my time.
1. The combat changes a lot from title to title, but there's plenty of variety on how to dispose your enemies with special attacks, regular attacks, using the environment, using itens and more. It's one of the high points in the series.
Bosses will depend on your skill. If you're good, you can clean the floor with the quite quickly. If not, some of them can become nuisances. And that's something that happens with pretty much any game. What you need to know is that the battle system will always give you many options on how to deal with any enemy.
2. Each Yakuza game is a stand-alone story using recurring characters. You can jump pretty much in any title and you will be able to understand the story. Some of the games have recaps for the titles before it, making it easier for newcomers to play. This should also explain on why it would be okay going through 0.1.6 which are the ones available on the PS4 (though, playing 2-5 is great too).
Yakuza 0 is a prequel to the entire series, so it's one of the best games to start. As I said before, each game is a stand alone story and, as a characteristic of the series, the characters are very well developed along with the crime story line.
It's difficult to pinpoint what Yakuza story is because it's campy sometimes, sometimes funny, sometimes serious, sometimes unbelievable, but even with this everything it's still a coherent product.
3.4.6 are just baseless complaints. OP brought a lot of videos which you can see and should take care of the showing part. The rest you should take a minute or two to read.