The point about the robots getting better seems to me to be a particularly important one. At some point the communications lag should matter much less as these robots become more autonomous. And there is a lot of money and talent these days going into the development of autonomy (the obvious example is in self-driving cars, but there are other examples). Many of the advances in those technologies will likely be applicable to space-exploration as well.
Of course, things may be advancing slower than some have hoped, and we won't have fully autonomous Mars rovers launching tomorrow. But building an infrastructure for manned exploration is also not something that can be done overnight. If we expect major gains from manned exploration because humans are better explorers than robots, or because communication lag extremely limiting, we might find those gains evaporate by the time a manned program can actually land people on Mars, or put them in orbit to control robots on the surface.
(Even if those gains actually exist, which, as theprestige notes, may not be the case)
I'm still less opposed to manned space exploration than this sounds. For instance I'm hopeful that we can get a robust space-tourism industry. An Apollo 8 style trip around the moon sounds pretty awesome. And if that includes at some point Elon's vision of sending paying passengers to Mars to set up shop there, great, though it's pretty hard to see how the economics can be made to work, at least any time soon. But as for prestige missions of just landing humans on Mars for the sake of going there... I don't know. It sounds like a cool thing to do, but if we're choosing between that and sending fifty rovers, I'll choose the rovers. Hell, I'd rather we send some telescopes to the solar gravitational lens than land humans on Mars.