Yeah, all good points about modern technology making the whole secret identity thing even less plausible.
With Superman, are two main things that we basically have to assume are not very developed in the DC Universe- facial recognition technology and satellite or advanced aerial surveillance. Superman makes all kinds of public appearances (Appearing in news footage, on smartphone cameras, police body cameras, etc.), and would appear on security camera that are used as evidence in trial (When the crooks he catches are prosecuted in the legal system) all the time, while Clark is presumably captured by CCTV, has a driver's license, and perhaps even has his picture run in the newspaper regularly in continuities where he's an editorialist. All that would seem to need to happen is one cop to have a computer run a facial recognition scan match of Superman against their archives and they should be told he and Clark Kent are at least identical twins and probably the same person- and that cop would have probable cause to run a scan because a lot of what Superman does, since he is not an authorized law enforcement agent, is technically illegal- it's understandable why everyone turns a blind eye to to it in-universe and doesn't try to arrest him, but they wouldn't have any trouble justifying privately running a facial recognition match (They might need to get a court order, I'm not sure how that part works.). Heck, I'd think the FBI would be very interested in who he really is for various reasons, even if they choose to let him basically do his thing unimpeded.
Similarly, Superman is always flying around various places, sometimes changing as he moves. One would think that between satellite and aerial surveillance could be traced back to it's source and maybe even slowed down to see him switching into or out of his costume. At minimum, though, they should at least be able to trace his flying routes back to their launch points. No matter what efforts he takes to obscure them, eventually, there would almost have to be a pattern of a ton of them being in and around Clark Kent's apartment and the Daily Planet offices. I mean, sure, he's "friends" with Clark and works a lot with the Daily Planet on stories, but after a certain point you'd realize that he's at those two locations way more than anywhere else he could conceivably live and work. Also, everyone would know exactly where the Fortress of Solitude is (At least the governments of the world's largest powers would).
I remember during the relatively short lived Superwoman monthly that featured Lana Lang as Superwoman,
they said that she had some sort of power or technology that subtly obscured her face so that it could be captured on video or film. Superman's never had anything like that mentioned, and he gives a lot of press interviews, including to television, that are key story points, though. In theory, the source of Lana's power initially was inheriting the new52 Superman/Superman Red essence when he died, later retro-conned when they did the Superman Reborn arc that reunited Superman's "two halves" and rewrote the timeline retroactively, so we could say that her power (If it was a power and not a technological device) could be something Superman had or has, but the problem with that it is that it was never mentioned in the New52 Superman continuity leading up to that run, or the Superman Reborn continuity that came out of it.
I think the most plausible way to handle that stuff is to say, essentially "The DC universe is already clearly not the universe we live in. You may notice that we don't have costumed superheroes or many of the big cities they reference, or open knowledge of and contact with aliens. Other differences are that that universe has not developed very advanced DNA, facial recognition, or surveillance technology." (Maybe that could even be explained by Wayne Tech and whatever that company the Green Arrow or his father owns secretly making sure to retard it's development behind the scenes and offering any scientist or engineer elsewhere on the verge of developing it a big check to come work for them and not develop it.). However, they'd have to take pains to adopt that line-wide consistently. Though I can't think of any examples off the top of my head, I think we've seen that they *do* have all those technologies in current comic continuity.
Of course, Marvel has had great success in movies basically ditching secret identities, and I suspect what they are doing with Superman revealing his identity to the world in the comics is a trial run for future Superman movies (Either handed down by WB to DC Comics or just a coincidence that DC Comics is trying something that could be of interests to people involved with future Superman movies. In recent years, the comics have often been talked about as a testbed or a way of generating ideas for television and films, and we've seen a lot of DC Comics stories adapted for the Arrowverse shows. In fact, Flashpoint is about to be done for a second time- it was done on The Flash TV show (Sadly, no New52 Superman in that one- this was before the Arrowverse crisis, when Flash's earth had no Kryptonians, before Crisis merged with Supergirl's [and by extension the Superman and Lois] universe retroactively so that they'd always been the same earth as far as anyone but the main characters, who got both sets of memories thanks to Martian Manhunter's intervention, knew.) and is the basis of an upcoming Flash movie (I hear they are either altering it to include a bunch of parallels universes or perhaps alternate timelines while Flash tries to get things back to what he remembers, or tries to create his "perfect" timeline, which is letting them do things like give the Michael Keaton Batman at least a small role. I think it'd be cool if they at least gave a small cameo to a Superman who looks like the New52 Superman was drawn and has the full costume with the high collar, hand coverings, Kryptonian body armor, original New52 harcut, etc.. I'd settle for him even just sort of flying by for a few seconds.
He doesn't even have to have a speaking role.
I doubt they'll do it, though.).