Just because it's all now phrased as bonuses doesn't change the fact that compared to the human baseline, most other races are "+1 to one ability score, -1 to four ability scores".
Now, the specific construction of the standard array reduces the impact of that. But in random-rolling it can have more of an impact, and in point buy you can create heavy-on-odds arrays like [15, 13, 13, 13, 11, 8], [15, 15, 11, 11, 11, 8], or [15, 15, 13, 11, 9, 8].
Humans are described in the game as being the most flexible of all the races. They are also the baseline for other races to compare themselves to. Therefore, and I know this opinion might be unpopular, but they should be bland.
I think having bland elements in a game just... sucks.
There are games where humans aren't bland and don't suck for a variety of reasons, and in those games sometimes humans are the most flexible, sometimes they are not. But they have reasons to be interesting.
Certainly, the mechanics of how humans work in 5e are really uninspiring. Any inspiration has to come entirely form the player and GM, which can be contrasted pretty heavily against well, any other ancestory in 5e.
This might simply be a consequence of how you don't make any further choices about your heritage after character creation, however.
Are Humans the most mechanically boring? Probably.
But so what?
Do one of two things:
1. Don't play Humans at all.
2. Don't let players play ANY species but Human, and bye bye Human Variant. Every single char starts with 27 point buy, and chars develop organically, over the levels.
Select an attribute. When making a saving throw, ability check or attack roll with that attribute where you do not already add your profuciency bonus, instead add 1/2 of your proficiency bonus (rounded up).
PHB Humans are the most mechanically boring race. How do we fix this?
By being humans! We are all human players (unless there are any Skrull changelings out there among us. If so. Welcome!). The range of emotions, backstories, motivations and skills that may guide us, move us, engage us, and shunt us to the front of the line must make for some amazing stories.
The vast and unending scenarios that we can imagine in our greatest dreams and worst nightmares should give us; the role-player, more than enough ammunition, energy and emotional thrust to to play out multiple facets of anything the human brain can conceive.
This is Spart....escapism. or Therapy or any other thing that D&D means/provides for you.
Boring? Never. Not so. Challenging, Draining, Frustrating, Emotional, Driving, Exhilarating, Accepting, Pre-judging, Short-lived, Spiky, Bashful resentful, Intimidated. Or just plain you. of Course, but boring? Only if you let it be so. And you never should!
Being Human is difficult when others can see in the dark, are more fortuitous, have greater resistance, can Jump like Hulk, Fly like Superman, Deceive like Mystique, and live to a thousand years old. The light that shines twice as bright etc.
Take your destiny. Make your stand. live to the fullest. And show those that live 20 times your age what you are made of.
Mechanically boring?.....Bollocks!......Live for now! Make History!
Rant over. Now go play the snowflake teleporting, hard shell AC, lucky, wall crawling, long-lived, long-armed, spell resistant, winged, armoured, shape-changing races.
What do they know? Sweet F/A, Nothing, Nada. Why? Because they are not human. Mechanics be damned! Well Rant may now be actually over now.
Just got done a session where it was ALL Humans, except my Halfling outlier. The entire session dealt with moving through cold water, across rope bridges, and dealing with Undead that popped out of the shadows. We had to deal with umpteen Con saves, Dex saves, then ability checks at Disadvantage because of Exhaustion due to the cold water. We also had to figure out how to make a fire to dry ourselves out with almost no wood. It was AWESOME.
It was true D&D at its finest. And not one Flying Kobold. or a Ninja Turtle in sight. Humans mechanically boring....how about the DM and player lack imagination.