One reason I disagree is that Dota (and Starcraft 2) are both games of imperfect information (more like Poker than Chess or Go).
That means a lot of the time, the game revolves around deception and subterfuge. If you've ever had to hunt down an enemy splitpusher and have to decide between spending 10s checking a hiding place and having a chance at getting a potentially game-winning kill, but also having a chance of not finding them and wasting your time, you'll know what I'm talking about. There's no optimal strategy, because all strategies have weaknesses to be exploited (e.g. In BW, if Terran knows you as Protoss always go greedy such as 12 Nexus, they can punish you with BBS. However if you play safe, they can play greedy themselves with 14CC, so there are a lot of mindgames.)
After AlphaZero's victories or DeepBlue's for that matter, professional Go and Chess players could find no weaknesses. Nada.
After OpenAi 5 became available, a professional player compiled a list of 20 weaknesses that I'm not certain OpenAI can ever fix (see link above). How do you tell the neural net when to dust or ward?
The same story with DeepMind's AlphaStar. Despite playing a good macro game, players online have figured out lots of ways to cheese it (e.g. send just one unit will cause all workers to be pulled and stop mining). I understand Poker's been "solved", but these computer games with much larger action spaces and imperfect information might turn out to be significantly harder to pin down than Chess or Go. There are enough edgecases that it's a much better representation of real life problems like self-driving cars (negotiating a merge for example).