I disagree. I mean, yes, I wish they had introduced fewer and slower, and some had never been released (yes .sucks I am looking at you, among others!).
But I disagree that a large number of new extensions cannot coexist. I think it is possible, in fact I have anecdotal information we are already there, that those outside the domain industry may come to assume that most reasonable words are an extension and guess one.
Also, I think startups will begin to look at what is available when they first name accordingly. For example, you are starting a venture fund. You see that .ventures is a TLD. You get Name.ventures and name your company formally Name Ventures. I agree we are nowhere near there yet, and that in US and in some other parts of the word there is an assumption companies will be on .com, but I think it is at least possible that will happen.
While I said in another post I hope ICANN pauses before any new approvals, because way too many were introduced, but I don't see that only a few will survive.
What is needed is more real organizations using them effectively. That will add respect. Some new gTLDs have done much better than others in this regard.
I think also that new gTLD could learn something from the restricted legacy extensions like .aero and .coop (originally .pro was one as well). If you have a very specialized extension it might make sense to require use by those who have status in that field. This is difficult to enforce, however, and would push domain investors out of that TLD, probably.
Bob