I'm immortal (6k MMR) and agree with the parent. I used to think similarly as you, because my mechanics were very good, but as I started to play with friends who are much lower ranked, I noticed that they can often execute things (e.g. ability usage) pretty well, but their overall play and strategy is desperately lacking. Things like playing the wrong areas of the map, spending their time inefficiently, never capitalizing on their strategic opportunities (e.g. not playing where they have vision, not playing in areas of the map that are near their objectives, not taking calculated risks based on available information).
I do think OpenAI five derived some of their advantage from seamless ability usage, and inhuman coordination in lane, but it also did some novel things strategically, that challenged some of the established tenets of high level play (e.g. they had a lot of mobility on the map, back when that was considered very inefficient).