Like a few others have said, it's not quantity, but quality that matters. The Fizban's Treasury of Dragons' Dragonborn have just 3 racial traits: Elemental Resistance, Breath Weapon, and a unique feature based on their "Family" of dragons (flight for Gem Dragonborn, a special Breath Weapon for Metallic Dragonborn, limited damage Immunity for Chromatic Dragonborn).
Just 3 mechanics. That's really all that sets them apart from a "normal" D&D person. And, at least in my opinion, that's easily enough to make Dragonborn feel like their own thing. They breath like dragons, resist certain damage types like dragons, and have a special ability based on the dragons they are related to.
The same is true for Changelings. Changelings basically only have 1 mechanical feature that sets them apart from other races (Shapechanger), and it's easily enough to make them feel "right" as a race.
The same general pattern also applies to Kalashtar (Mind Link, Mental Discipline, Dual Mind, Severed from Dreams), Shifters (Darkvision and Shifting), Aarakocra (Flight and Talons), Fairies (Fey creature type, Fairy Magic, Flight), Goblins (Fury of the Small, Darkvision, Nimble Escape), and a few other races.
However, there are also quite a few races that do need more mechanics to set them apart from the "assumed racial mechanics" of D&D 5e. Warforged have a lot going on (Poison Resistance, not needing to eat, drink, sleep, or breathe, immunity to disease, shorter long rests, +1 to AC, taking an hour to put on/take off any armor, armor can't be removed against your will while alive), as do Elves (Darkvision, Trance, Fey Ancestry, Keen Senses and a subrace), Grung (Climbing Speed, Amphibious, Poison Immunity, Poisonous Skin, Standing Leap, and Water Dependency), and a few other examples.
The amount of mechanics depends on the race and what sets it apart from the base D&D race. Some races need more mechanics than others (Warforged and Grung), and some really don't need all that many to explain their concept and make it playable (Changelings and Dragonborn).
Quality versus Quantity and context is everything.