Abundance and organism mass is complexity scaled to a linear thing? I think not. Complexity looks more like scale invariant. You'd think it woud be simple, linear, and we can choose things that do that, but this chart does not measure complexity. It measures scale.
Abundance and mass is not complexity. If anything, the protist stage, the mechanics of archaeon or bacteria, are far more complex than a human society consisting of a few billion people, a few quadrillions of cells, a few septillion molecules.
True, our human biofilm is getting big, our infrastructure trillions of pounds to one pound of flesh, but there are structures far vaster on Earth (made even vaster if scaled up to our size). Protists and fungi enjoy global connectivity. There is evidence that life goes right on down to the mantle, and could outnumber surface life to be the majority of species on Earth. There could be a plate tectonic network for all we know. Point being, complexity is scale invariant. Complexity is a dimensionless constant.
Looking at the chart, what I get is maybe we are too small for aliens to notice.
No mosquitoes this summer. True, we are in drought. But the alarming number of murder/death/kill lawn companies, with little yard signs showing mosquitoes in anguish or death, has reduced insect populations. That's alarming.
I had one lone mosquito appear out of nowhere while I'm on the couch. She was a her and bit me. I let her feed. I took her outside on my arm and waited until she was done eating and flew away.
(I am a shoo bug instead of a kill bug, escorting bugs out rather than smoosh them. I don't think its a moral or philosophical choice. It's a respect of life that life shows life. Naturally. Therefore, I only kill when classified vermin).
When I was a kid, the planets of the solar system were smudges on photographs taken by telescopes. People didn't know what it looked like, so they made shit up. I do know a lot of people beleieved other people lived on those other planets. I drew pictures of what the people looked like. The people of the Sun were always fire and lightning bolts. Mercury a clown face sarguaro cactus. Venus obviously a blonde. Mars little green man. Jupiter and on were tough to do and varied on who looked like what.
It helped a lot that we explored space with robots and found out what's really going on.