Add me to the list of people with deep disagreement.
If the BBEG makes his big speech, and every other player at the table can guess what my character will say in response, then I have played a consistent *personality*. If, at the same time, each player draws a significantly different *illustration* of my character, though, I am 100% fine with that outcome. "But you never established via role-play that Boris has green eyes!" Yeah, live with it, buddy.
Let's say we've been playing at the same table for a year, and you've noticed these things: My character habitually defends the helpless, cures the sick and heals the injured, and sometimes accepts the hospitality of a commoner whom my character has rescued or healed. Whenever we're at a tavern, someone says "Hey, that's Boris the Green! I know a song about you!", and I say "Yeah, I'll have a drink and sing along". I challenge foes before striking, offer the enemy a chance to surrender, never lie, and only cast Zone of Truth when everyone in the AoE consents (and agrees to answer each other's questions). When I cast Find Steed, I got something which looks more like an animated rough-hewn sawhorse, than like a stallion or mare. I hunt for game when the party's on the road, and I make my own javelins and arrows with woodcrafting tools (though I buy the metal points). You can reasonably infer that I'm playing a Paladin with the Oath of Ancients and the Folk Hero background.
If you consider this a cypher then (shrug) too bad for you; it's good enough for many DMs and many players.
If you have no idea what anatomy is under Boris's chainmail, nor whether Boris would bear children or sire children, then I have played an *adventurer*, not a gender stereotype.
If you assume that English is the DM's first language, that's on you; no one owes you an obligation to speak with enough of an accent that you can tell what their first language was. Likewise, if you assume that Common is Boris's first language, that's also on you; I don't owe you an obligation to have Boris speak with an accent from Draconic or Elvish or Infernal, and if you're baffled by a non-human whose behavior falls within the range of behavior you expect from humans, then that's yet again your problem, not mine.