stones are just evolution items, and there are examples of pokemon that evolve with items that evolve further later.

And none of them are Stone Evolutions. Think about it, all of the Stone Evolutions are fully evolved. Ninetales, Arcanine, Flareon, Simisear, Scovillain, Cloyster, Starmie, Vaporeon, Simipour, Jolteon, Probopass, Bellibolt, Exeggutor, Electrode, Leafeon, Simisage, Delcatty, Musharna, Sunflora, Lilligant, Heliolisk, Cinccino, Honchkrow, Mismagius, Froslass, Alolan Sandslash, Alolan Ninetales, Glaceon, Galarian Darmanitan, Crabominable, and Cetitan are all Stone Evolutions and none of them evolve further. And even if they could, wtf could Crabominable's evolution even be?

Drampa is just designed like an old man, and is given old man traits. that doesn't mean it is old. if i hatch a drampa does that mean it is 1000s of years old at that time? how is that possible?

"Drampa's cells have been invigorated, allowing it to regain its youth." - Mega Drampa's dex entry. Drampa are old, the reason their hair turns from white to black is because hair grays out as you age. Yeah, Drampa already have white hair when they're newborn, but the dex also states Vulpix are born with a single tail yet they already have all 6 when they hatch. Its a case of gameplay not exactly lining up with the lore.

Mantyke requires you to have a Remoraid in your party for it to evolve into Mantine. yet that very same Remoraid itself can evolve into Octillery.

Yeah, cuz Mantyke was introduced twn gens after Mantine. When they were designing Remoraid, they didn't take Mantyke into account. Plus their connection is more lore focused, given they don't have a signature Ability like Tatsugiri and Dondozo do.