How? Do these 5 companies even operate in the same places? Around here we have DoorDash, Uber Eats, and that’s pretty much it. We have SkipTheDishes, which was present before the other two outside urban areas, but I don’t even bother talking about them, most restaurants in the area have switched away from them. The other alternatives just never existed outside highly urban areas or have simply been pushed out by the bigger players. Where are the effects of this highly competitive market, exactly?

Depends on the geographic distribution of the companies. Meituan is huge, but they don't do shit in Europe or the US.

There are probably areas where these companies operate as effective monopolies or two-company oligopolies.

Split the world us/china/other and ignore minor players and there are 1/3/1.

In a given are there is competition but the local competition is likely to be pushed out by Uber Eats who could undercut them out of business for a while. Or just have better tech / customer experience due to scale (looking at you Menulog)

It’s more of a cartel if anything. Each owns a certain geography