A hero is someone who puts himself in harm's way for the benefit of others. A guy in a desk job is not a hero.
In the modern world, all large battles are fought out behind desks.
A researcher who gives up a $200k job at a large IT company (e.g. Google or Facebook) for a measly paid job at a university to work on a project with eventual high societal impact IS a hero.
Re: battles. There are still real battles in the world (Ukraine, Syria) where there's plenty of heroes.
To sum up, I'd say that it's a blessing that a lot of the world is so peaceful now that the meaning of the word 'hero' is getting washed down to literally 'people doing their (maybe slighly unpleasant) jobs'.
I think you're right that most people that work in a contractual fashion with a money payoff should not be considered heroes, but it's also not true that only people who go to war should be considered heroes. Rosa Parks (and the less famous women who did the same thing and preceded her), for example, are certainly heroes.
Not every activist or revolutionist is violent. Sticking to known examples: Gandhi is another excellent non violent example. Sticking to politics, Nelson Mandela. Mark Felt, also a whistleblower. More recent examples are William Binney, Edward Snowden, Julian Assange. These are my examples, of people I consider heroes. History will decide who the public's heroes were.
These people go against authority, often get ignored or bullied in return, including loved ones and relatives. Like the poster from Fargo, "What If You're Right And They're Wrong". It indeed takes great courage and often sacrifice to go against the tide.
That support employee who's ignoring his protocol and is risking a sneer (or worse) from his boss, the one telling you truth while he's now allowed? He's performing one heroic deed. If its a pattern, we can speak of a hero.
Also, IMO military service is a lot more gray area than black and white when viewed in cultural and societal context. I've known several active and veteran members of a few branches of the US military, and while I commend their skills, I don't think many of them would describe everything the US asks them to do as "heroic". A sizable fraction of the current world mess is the fault of the governments currently fighting it.
But all of this is barely relevant to a discussion about what might be termed everyday heroism.
I did not used to hear the word "sacrifice" a lot. I hear it a lot now. I don't like it as a standard of behavior and wish it would stop.
Was your grandpa that fought in WWII (assuming for a second you had one) a barbarian?
Fighting doesn't make one a barbarian. The belief that suffering and sacrifice are the path to glory are.
Is it barbaric? Maybe, but, whether we like it or not, the world has a defnite component of barbarism to it. There are wars going on as we speak, and there are threats of much bigger wars constantly hanging in the air.
It not impossible to eliminate physical danger out of our lives and to dismiss it (because one does not witness it first-hand at the moment) is not very mature. I'm not even mentioning the natural calamities, fires, car crashes etc., where there's room for heroism as well.
I'd just prefer to see no sacrifice of any kind, especially on my account.