No worries! See above for a pretty good rundown! The general point is that TSR era D&D had very different play expectations baked into the game. 3e/4e/5e assumes the characters are 'heroes' from the start, and that they're special snowflakes in the game. Earlier D&D assumes that the characters are largely nobodies at the beginning of the game, and their aim is to delve into dungeons and other dangerous situations to make some coin in an uncaring and harsh world. There's more to it than this, but that's the basics. Did every table play that way? No, but that was the default.
In TSR era D&D, various races had class level maximums as well as hard racial caps/minimums on ability scores, partially because of Gygax's desire for a humanocentric campaign world, partially to enforce genre conventions at the time, and partially as a way to 'offset' the racial special abilities that elves, dwarves, etc got. In return, demihumans were able to be more than one class at the same time, generally getting the best benefits of each one.
Ability scores were generally scaled on *human* averages, meaning the average human will be stronger than the average halfling, or the average elf will be more agile but less hardy than the average dwarf. By taking racial limits/bonuses away from the various races (ie, halflings can have an 18 strength, half-orcs and dwarves can be wizards, etc.) the game is essentially putting all races on the same scale, and making elves 'humans that don't sleep' or halflings 'short humans that love food'. The root of this issue is that due to 5e's design, a race that cannot have the max in a given ability score will by default be a suboptimal choice for a class that needs that ability score, so in order to make every race/class combination 'viable', they should all have the same statblocks.
I simply don't find that interesting - they way elves, orcs, and dwarves think and experience the world should be completely foreign to a human, and to one another. Orcs are evolved to aggressively expand their territory for the orcs, they don't have the same drives and morality that humans, elves, and dwarves do. Does that make them 'evil'? If the definitions in your game's system of morality (ie, the alignment system - let's not get into how it used to be derived from cosmic forces) comes from a human outlook, then it probably does.
As far as the 'randos' comment - the default assumption of a 5e D&D game for a 'modern' online player (when I say that, I'm talking about the very vocal, terminally online D&D redditor types) is that the game is going to be heroic, that their character needs a significant backstory, the game is generally narrative/quest driven, and that their character isn't going to die without their input/consent on it. No this isn't everyone, but these are the people that have a voice in the direction of the game, because they're the most vocal. "Fun" is a subjective term, and if someone is having fun, who am I to tell them they aren't allowed to? My issue arises when the game is greatly changed to make the vocal minority stop complaining.
Sorry for the wall of text - this is a sore subject for me. If you're interested in an older-school style of play, check out
Principia Apocrypha for a pretty decent example of how those games were played. I have real concern that the big jump in players due to stuff like Critical Role (I met a guy with a tattoo of a full set of polyhedrals, wearing D&D pins, etc. that *has never played an RPG*) is going to shape the hobby, then that group will just leave once the fad dies down, leaving the industry in a rut again.