I would argue there’s still a difference between “callous because medieval life sucks” and Viking “plundering as the core value”. Viking is a profession after all, not an ethnicity.

Mongols are a bit different case, as I would argue the idea of Mongols that exists in popular culture is pretty far off, and fits better to earlier steppe cultures - Cumans, Pechenegs, etc. By the time Mongols rolled into what is now Russia, the Golden Horde was an empire. With massive production capabilities, logistics, the works.

That said, I agree that the level of everyday violence and cruelty of those periods is severely underestimated