in dota the tactics is to do with the execution of abilities, often times in coordination with other agents in execution of their abilities to get combo effects while adapting to the situation as it unravels.
As an avid dota player I wouldn't agree with your characterization that 70% of dota 2 is your definition of tactics. What I've noticed differentiates player MMR the most is the strategy applied to each context. It's rarely the execution that's the problem as you can gain such overwhelming advantages through strategy.
There's barely any long term strategy in Dota, only meaningful strategic decisions are items and heroes. Even ultimate usage has like 2 minute window of importance. Wards too. And maybe the decision to push high ground because of how many times games are lost because of it, but it's the tactical errors usually making most of the difference there.
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).
