I claim that we don't. I mean, it's way too ambitious goal to set universal definitions like this, and this is not the point anyway.
> 2. definition of journalism / journalist
Whoever who likes to be called one. This is the silliest proposition, I don't care the slightest of what do you tell a girl when she asks what do you do for money, usually I don't even care who you are at all, I just care if reading stuff on your resource adds value to my life. It's not a honorary title, for goddamn sake, you are not (or rather, unfortunately, you should be not) entitled to anything because you "are a journalist". I care only for what I read, and you (a news portal/journal or a person working for such an entity) mostly care about if what you publish brings you money, and maybe for some artistic matters that make you believe it's your "purpose" or whatever.
So: maybe possible, but not useful.
> 3. full disclosure about what is news (objective) and what is op-ed
Useful, but absolutely impossible. I find a way to publish a story about unicorns fighting dragons in the Singapore and call it news, because I'm fucking Salvador Dali and you won't do a thing about it. And if the country we live in makes it possible to sue me for that, then it's the worst form of censorship possible and basically it's just a shitty country.
> 1.definition of news
Given the 2 and 3, and the fact that your wife or your local farmer might care that you ate eggs for breakfast: both impossible, not useful and yet already solved somehow. Readers eventually buy what they feel (maybe just because of marketing, but still) adds value to their lives (and part of it is news, defined as "facts being of interest to the specific person"). Writers (journalists, if you will) eventually are somewhat forced to write stuff that people will buy, and since some potential users are interested in "news" (i.e. basic facts w/o much of an interpretation being of interest for them), there is an incentive to make such content. So, basically it's THE job of a journalist (defined as "any content maker at all") to find out what is interesting to a specific audience (both facts and op-ed pieces and stories about unicorns) and make it.
So, defining what is the news for your audience is difficult and yet, honestly, I think "journalists" are pretty proficient in finding out what that is, because, well, market economy. The problem with making quality content is not that nobody knows what people want, there just is too little incentive to make quality content, because you only care about larger audience, and the way to sell to larger audience is basically just marketing. At some point, it doesn't even matter that much what you write as long as enough people recognize you as "the source of the news".
After all, I only want to be notified about stuff I actually care about, it may be something that happens once in a few months, plus maybe some very specific stats every day, plus some "op-ed" stuff that is mostly written by actual professionals in their actual industries (which obviously pretty much never can be "professional journalists", simply by definition). In short, what I (and most people) want is expensive to make, and after you make it, you will find hard time selling it to us.
TL;DR: "they" make shitty things, because "we" buy shitty things, and there's no way around it, no matter how hard you try to "define" anything.
P.S.: when I say "buy" I don't necessarily mean literally buying, it may be viewing ads or whatever form of monetization the resource makes up.