The alternative would be to either go completely insane trying to reconcile the inconsistencies in the stories or just write all of it off as crap. Personally, I like being able to enjoy each thing for what it is.
But, why is a the idea of a multiverse needed to read a comic (or watch a show) as it is?
The multiverse idea is primarily a crutch to allow obsessive fans to easily reconcile everything if they really want to "make it all fit". But, it is not needed.
From 1986 to 2006, DC had no formal multiverse. In fact, they specifically ruled the idea out. (Every so often, a writer would try to sneak the idea in. But, the only two sanctioned examples were Morrison's "Earth 2" and Byrne's "Pocket Universe". The later was a quick-fix that was destroyed immediately after it was used.)
DC never once felt the need to reconcile then current comics with "Batman: the Animated Series", the Burton/Shumaker "Batman" movies, "Justice League: Unlimited" or "Teen Titans Go!". DC never once tried to reconcile their "Elseworlds" books with mainline comics. (In fact, it was rare for an "Elseworlds" book to get a sequel, never mind to cross-over with another book.)
For the purposes of their comics, DC specifically ruled out a multiverse for decades, but never had problems publishing unrelated content.
The real question would be what happens to the time traveler in that scenario once they return to their own time. Do they return to their own universe, where the grandfather is still alive, or do they return to the future of the universe where they succeeded in killing him? Target: 2006 assumes the former, which is essentially how Hot Rod, Kup and Blurr, beat Galvatron.
Another take on this is that the time traveller is effectively isolated from the changes that they (or other time travellers) would make if they travelled to a point before the changes were made. "Crisis on Infinite Earths" was an example of this at first. (Later, it was less clear which characters were directly impacted and/or remembered.) The Terminator movies are another example, as Skynet is shown to be able to "remember" scenarios and circumstances across changes to the timeline, and is able to ensure its creation even after its original "birth" had been prevented.
Similarly, in TF, Furman's "Time Wars" assumed that the the characters who traveled through time were isolated from changes to the timeline. (Rodimus and the others left the year 2008 as the timeline was collapsing. When they returned, time had restabilized. However, history had changed significantly.)
I also don't believe that time travel is possible. I don't believe that we can go either forward or back in time and I don't think we could visit other timelines/realities/universes.
I actually travelled through time *and* space this morning. I left home at around 8am, and arrived (several miles away) at work roughly an hour later. (And, I swear that the local transit system exists in slow-time because I left at least 5 minutes early and caught an earlier train, but I nearly missed a connecting bus that always leaves at the same time.)
Going Mach speed means you're going faster than you can hear. But, when we're going that fast, we don't hear things backwards. we hear on loud sonic boom when we break the sound barrier and after that we hear normally. I believe something similar would happen with light speed. There would be a bright flash of light and then we would just be going really really fast. No special effects, no time travel, nothing
There is some evidence that gravity and speed influence the "speed" of time. But, the science for this (and observation impact on quantum/probability) is still very rudimentary .
There was even an acknowledgement on page that the two had essentially nothing in common except for the name but they were both regarded as "the" Smokescreen of their respective universes.
You are talking about "Transformers: Universe" #1. That was the first comic that I had to "count" purely because it was official, even though it read like fanfic. (I used to have a mutual friend with the artist, Dan Khanna. Khanna told my buddy that "Universe" was "Avengers Forever" with Transformers. In other words, "Universe" was derivative of another comic that in and of itself read like fanfic.)
I do not recall there being any mention on page about it being "Smokescreen v/s Smokescreen". If I am remembering correctly (and I can check later tonight), it was a visual gag that *everybody* and their mother picked up on.
(And, really, why should two guys with the same name have to be related in any way? There is a guy who works in this office suit who has the same name as me. The wrestling promotion I used to help out at had enough guys with the same first names that some guys ended up being known by last names or ring names for the sake of identification. Hell, when I was in school, there was another student with the same first and last name as me. But, in TF, when two guys have the same name, they are the same guy.....even across different universes.)