Okay....look.
A reboot is nothing more and nothing less than this. A change in the characters/universe’s history wherein they are objectively now a different version from what they were before. it doesn’t matter how big or small those changes are, if there are changes (outside of one particular circumstance I’m gonna get to) it is a reboot. Zero Hour was a soft reboot. Crisis on Infinite Earths was a hard reboot. But they were both reboots, it didn’t matter that the post Zero-Hour universe was very similar to the pre-Zero-Hour universe.
I’m not talking about retcons, those are different.
Norman Osborn being alive after being dead isn’t a reboot because in the same narrative which stated he was dead clear cut explanations were provided detailing how in fact that wasn’t true.
Compare and contrast to say Crisis on Infinite Earths. Superman pre-Crisis was Superboy, saw his parents die, battled his childhood friend Lex Luthor who grew into a mad scientist. Post-Crisis he became a superhero as an adult when he came o Metropolis, his parents were alive when this happened and remained so for years thereafter, Lex Luthor met him when they were adults and was a corporate tycoon not a mad scientist.
It wasn’t as if we were following Pre-Crisis Superman’s narrative and then suddenly there were in-universe explanations telling us Luthor had actually always been a businessman, his parents had always been alive and he’d never been Superboy.
Different versions of the same character with a different history.
Spider-Man in One More Day is the same way. Pre-OMD Spider-Man married Mary Jane, they had a miscarriage, he met Mephisto and sold his marriage. Post-OMD Spider-Man missed his wedding, he and MJ presumably never got pregnant, he never encountered visions provided by Mephisto and never was made an offer and consequently he made no deal.
They are two different versions because they have life experiences which are not the same, although obviously if there was an Earth 617 Spider-Man with the exact same life experiences he’d be a different version too because he wouldn’t be from the same universe in the first place.
You can technically apply this to other Marvel time travel stories as well, such as ASM #500. In ASM #498-499 Spider-Man fought alongside other heroes and their accidentally brought Dormammu to Earth, which then led to Spidey travelling in time, winding back to moments before this happened and preventing it. Technically speaking everyone but him was now a different version because they lived a different life, one where Dormammu never invaded. However, I think for stories like that it is very different because the only things in the histories of the characters/universe that was changed were events that themselves were first established in the very story which was altering them.
That is to say we shouldn’t regard the Cyclops of post ASM #498-500 as a rebooted version because everything that was changed in his life after ASM #500 only happened in ASM #498-500 itself. It’s like something that was self-contained.
So with all this said...WAS the Marvel Universe:
a) Rebooted and now has a different history which you could witness if you time travelled backwards through any characters timeline
b) Was destroyed and the character we are meeting now are new creations based upon the old one, so no better than dirty clones
c) Actually the EXACT same versions of the characters we’ve been following since the 1960s but they simply died and got resurrected and shuffled around. E.g. the Doctor Doom appearing in Invincible Iron Man in late 2015 wasn’t a Victor Von Doom with a personal history different in some way from the pre-Secret Wars Doom. Nor was he a new version of Doom who shared a history/memories identical to the original man who’s story ended in Secret Wars #9. He is the EXACT same guy who played God in Secret Wars #1-9, who got beat by Richards and just got transported to the recreated Marvel Universe with a fixed face and no memory of what happened. Same deal with Tony Stark. He categorically died in the final incursion in Secret Wars #1, but just got brought back to life either by Doom (hence he was in Ultimate End) or by Reed and Molecule Man, and doesn’t realize what happened.
d) It’s still too early to tell.
I haven’t read EVERYTHING Secret Wars related or everything following in the wake of it, but based upon what I have seen I think options C and D seem the most likely as of this writing.
Allow me to elaborate.
Multiple characters Post-Secret Wars acknowledge and remember the events of the Incursions and in some cases Secret Wars itself. The Squadron Supreme book to my knowledge is literally BUILT upon the back of their worlds were destroyed. The Ultimates book makes it clear that people can’t remember exactly what happened 8 months ago and that the universe has been ‘renewed’ (not rebooted, renewed) resulting in a new isotope (or something) showing up that wasn’t around before. And they know that it didn’t previously exist, which is to say they are acknowledging the pre-SW state of things that they clearly remember living through.
Also, Silk in her second volume is interacting with her younger brother whom she discovered in her last vol 1 issue, an issue which was all about her dealing with the chaos of the final incursion hitting Earth. In other words, for Silk to be interacting with her brother that issue MUST have happened and so she MUST have experienced the final incrusion.
Additionally Web Warriors has the heroes of that series working together as a result of the Spider-Verse storyline from 2014, which again ONLY happened as a tie-in to the Incursions. Spidey-UK in that series is in fact still in mourning over the incursions killing his world and everyone he knew so they DID happen. Furthermore the roster of the Web Warriors is identical to the characters featured in the Spider-Verse mini-series during Secret Wars, where they came together as a team in the first place. The only difference is that Mayday Parker is also a part time member of the group, but she is sporting her new costume which she got in the Spider Island back up story from Secret Wars. That back up story which ALSO featured the Uncle Ben Spider-Man from Spider-Verse and had her clearly remembering her father’s death in Spider-Verse. Uncle Ben Spider-Man is also set to appear in Web Warriors.