Disclaimer: I am not an American

I found this interesting though, so I am going to comment on a couple things.
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1. What do you start with in D&D? Well, technically stats - which is worse - but primarily your job (class). Your job tells you what you can do, and you can do nothing else. 5.0 expands this to your 2nd job (background), which is good, but what we like about some other systems is that you start with your personality, ...
First of all, as has been mentioned, "tells you what you can do and you can do nothing else" isn't really true. To start with there are feats, skills, proficiencies, multiclassing, etc that will spell out additional things a PC can do, other than what their initial class selection gave them.
Second, why in the world would that mechanical framework determine exactly what that character can/can't do? They might tell you some things that you are particularly good at, but they are not intended to be a comprehensive list of things that a PC can do.
Third and from a slightly different angle, asymmetrical play is definitely one of my favorite things about D&D, and classes have largely been the typical way in which that is done (in D&D). Classless systems (IME) have not been particularly successful at achieving this, largely due to balancing issues I believe.
2. In combat, you hit or you miss. If you are trying to convince someone or climb a wall, it's the same principle: a static DC - a number that defines whether or not you succeed or fail. Casting spells means they either 100% happen exactly like you thought - or you are out of [spell resource] and they do not happen at all. Everything is binary
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(D&D has crit successes [and you can add crit fails] but those are only combat rules and still basically binary.)
I don't really think things are as binary as you make them out to be. First of all, in D&D "an attack" is actually intended to be not necessarily a single swing of a sword but an abstracted amount of thrust/parry etc. so the hit/miss is an overall summation of the success/failure with damage determining the degree of success. As for casting spells, some of them also have save effects, so are even less of a binary proposition.
Critical success or failures (10% chance) as mentioned, are certainly not binary as well. As for being combat specific, this may be true RAW but many GMs IME still treat them differently outside of combat. Many GMs also treat skill checks as not necessarily binary, if more granularity is desired.
By contrast, in D&D you start with stats - which narrows what you can even choose to do with a job - or race - ditto - or just your JOB. This defines you completely; it's explicit. You can do no more and no less and you can't do X until level Y. You are a CLERIC: here are your assumptions. It's precise, and at least in some ways, restrictive / limiting. (Even multiclassing only gives you different jobs.) It's beautifully simple and again, if you think I'm saying something bad I refer you to Disclaimer, above.
Again, I am not sure why you think that things are so defined by one's class (which =/= job much more than phyla=job) I really don't think it is explicit at all and I would be very interested to know why you think it is. If you mean what spells you can cast, or how many attacks, then I would agree that it is
largely dependent on a PCs class/classes but that is only a part of what the PC can do.
5e doesn't really start with stats, in that pure rolling a character is not the default, regardless the only time I would start with a class would be if for some mechanical reason I wanted to try out that particular class. Otherwise, that is never how I make a character. We always come up with a concept, then determine which class best fits that concept. For instance, if it is a fighty type character it might become barbarian/fighter/rogue/ranger/paladin etc depending on which fits best and matches the preferred play-style for the player and game. It's just a mechanical framework though, not what defines the character. The stats are intended to match the concept, not the class, so they might not be ideal.
Ideals, bonds and flaws are very important as well, along with background as they often have more impact on the game and what the PC does than either class or stats.
I hope this doesn't seem "unconstructive" and if you want to add some granularity and/or reduce the degree of binary success and failure in conflict resolution then that's great. In fact, we do that a lot already in different ways.