One: as I said, the difference between our perception of "major" and "minor" discrepancies is often a function of how long we've had to rationalize them to ourselves and convince them that they're minor. I mean,
The Wrath of Khan has some huge discrepancies with TOS, like inserting Chekov into "Space Seed," turning Khan's multiethnic band that were stranded as adults 15 years before into a bunch of 20-something Nordic types, having the Starfleet paraphernalia left with the
Botany Bay be movie-era instead of TOS-era, retconning Kirk into an absentee father when he never gave any hint of having a son before, etc. Harve Bennett came from a time when continuity in series TV was expected to be loose and impressionistic, to keep the broad strokes but change details to suit your story, like the ways he retconned
The Six Million Dollar Man's continuity repeatedly over the run of that series. But we've had 40-odd years to convince ourselves those disrepancies are smaller than they actually are.
Two: Yes, of course some of the differences are more major than they were in the '60s, but that's only reasonable to expect, because the productions are made in different generations for different audiences. Naturally certain things are interpreted differently to tailor them to those audiences, whether it's incorporating more modern technology or eliminating the casual sexism of TOS. These are changes that
should be made, because creating fiction is a process of refinement and improvement. They're differences in how the imaginary reality is depicted by the storyteller, but the different depictions are meant to be of the same thing. If you ask an impressionist and a cubist to paint the same model, their paintings will be very different, but it's still the same model.
Again, the same as Marvel's pretense that the comics stories set today are in the same reality as the stories set in the '60s despite the characters having aged no more than 10-15 years. The details are adjusted to fit the times, but the
important parts, the events and the experiences that shaped the characters, are still the same.
That's where willing suspension of disbelief comes in. You can't possibly believe what you're seeing is real without
some suspension of disbelief. If it were real, there wouldn't be cameras around to record it. There wouldn't be music playing in the background. The characters wouldn't look like recognizable actors, or wouldn't change their faces and voices when they're recast. They wouldn't be delivering polished, memorized dialogue but would stammer and stumble more. They wouldn't all be so good-looking and well-coiffed. There'd be no sound in space and far less light. Plus, of course, you wouldn't be able to see it at all because it wouldn't have happened yet and there's no such thing as time travel. It's always obvious that it's not real, but as a viewer, you choose to ignore the things that make it obvious. So it should be just as possible to suspend disbelief about other things.
Also, "
suspension of disbelief" means it's temporary. Every story is real
within itself, while you're watching or reading the story. You adjust your suspension of disbelief to buy into the premise of the story you're currently enjoying, but afterward, you come back to reality, acknowledge that it's fictional, and understand that the differences between different fictional constructs are functions of artistic choice and creative process.
It's weird to me that you see it as a burden. Exploring how different creators interpret the same subject is part of what makes creativity interesting and fun. Think of it like listening to two different bands' covers of the same classic song, or watching two different theater companies' interpretations of
Hamlet.
And that's exactly what they're doing. Continuity, in this sense, is not about what the sets or costumes look like, it's about the events, the ideas, and the characters' journeys. Everything else is just presentation. If you can accept that Robin Curtis's Saavik is the same person as Kirstie Alley's, or that
this Vulcan is the same planet as
this Vulcan, it shouldn't be so impossible to accept that SNW's Pike and
Enterprise are the same as "The Cage"'s. The continuity is in the substance, not the surface.