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?

Without more context this is silly to say. It isn’t as if we know the natural or correct construction of this market a priori and that 5 is clearly a distortion from that. Consolidation can sound bad in the abstract but in this relatively immature market you could still expect major shifts to get to a steady state. Just a little bit ago people were remarking on VC-subsidized delivery; as that goes away, consolidation is not unreasonable.

Edit: ‘this’ in the original parent comment was along the lines of ‘five out of potential thousands of actors’

There might be some more specialized ones. I know there's a few more here that only work with Chinese restaurants and mainly advertise in Chinese.

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)