Presumably that wouldn't be the case for any innovative companies, though. There might not be Richard Bransons storming into existing markets and dominating them, but there would still be Microsofts and Googles.
emh doesn't mean everyone knows everything, it means the price accurately reflects available information. if an innovation was believed to be world changing, it would be worth a lot, if the belief changes, the price changes.
The economy is a faith-based construct. Prices aren't set by "information", but by faith in value - which is one of the easiest things in the world to lie about.
In EMH there is cooked in some notion of overall largely rational beliefs, and yet the shares trade hands from someone selling to someone buying - both of which feel they got a good deal worth making money from.
In fact if the EMH was true, then all hope for financing innovative companies would come from delusional investors making the sub-optimal choice of investing there. How “efficient”.
Why? Then how would be all your stealth companies supposed to raise enough money in the first place? Or attract customers?
In practice most companies are publicly known as early as series A at least and remaining unnoticed for longer requires lots of effort that would definitely hamper the growth of such companies.
And the market definitely takes rising competitors, even private, into account when assessing the financial prospect of existing public companies.
That definition of EMH seems to be what's causing this idea that innovation in new companies is impossible, rather than the general idea that asset prices reflect available information. Some information is not available, and that won't be reflected in prices. That's all.