Strikerkc, exactly what
Richard Baker said above. If continuity between the series wasn't that big a deal, Gene wouldn't have spent so much of the early days of TNG banging home that it was the same universe as TOS by bringing McCoy onto the new
Enterprise, by referencing TOS episodes... Even the re-use of TOS/TFS ship models, uniforms, and equipment ties them all together. From the airing of "The Man Trap" (Fox wasn't the first to air a series out of order) through Voyager's "Endgame", it's all one shared universe with internal consistency. They got most things right, and many of the errors are due to only one or two people who feel the same as you -- that continuity doesn't matter. Time-travel issues aside, I can point to only a handful of things throughout that entire thirty-five year span that Don't Work™:
• Mike (and later Denise) Okuda and their on-again-off-again research skillz (from
Constuitution-class registries to Kirk's birth year to when TOS is set -- I won't go into that essay here), that, unfortunately, newer productions adhere to.
• Ron Moore not knowing or not caring about the distinction between job (Transporter Chief) and rank (Chief Petty Officer) and making Lieutenant Miles O'Brien a crusty old enlisted man. I like the trope, I love the character, but let him remain an officer -- maybe even started out enlisted, got a battlefield promotion under Maxwell, and then he went to OCS, but not what we got.
• Scotty at the launch of the
Enterprise-B, seeing Kirk "die", and then after he comes out of his transporter stasis thinks Kirk came looking for him. That one's on Brannon "that was one episode -- who's going to care about that?" Braga. (He also wanted to make Zefram Cochrane a woman in First Contact to be Picard's love-interest for the film, people pointed out we'd met the guy in TOS, his response was a similar "that was thirty years ago -- who's gonna remember?", wiser heads prevailed, and Lily Sloane was written in.)
• The TNG films in general. I can grudgingly find ways to work with the first three, despite the
Enterprise-E, despite characters acting out-of-character (see: Kurlan
naiskos), and so on, but Nemesis is a hot mess all through. It needs a full rewrite to potentially even
maybe work, and is why I end my span with "Endgame" in '01 and and not Nemesis in '02.
Altogether, that's not bad for so many hours of content, on the production schedule they were under. Far more is consistent across those than inconsistent. Including uniforms. DS9 introduced the new "work uniforms" inspired by TNG's Academy uniform, but also still showed the TNG uniforms used for more formal occasions. TNG reciprocated by using the "Class C's" in Generations. Generations also introduced the new commbadge design that then went into use on DS9, and also in Voyager when it premiered shortly after. First Contact introduced the new BDUs and they then went into use on DS9 (and on the people back home on Voyager). And so forth. Not counting Valeris, we've only had a few minor uniform goofs across all the series.
And one thing that TNG, DS9, and VOY all share is glimpses of a possible future for each set of characters where the same uniform is in use by Starfleet in the respective time periods (2395 for "All Good Things...", 2422 for "The Visitor", and 2404 for "Endgame"). I don't necessarily hold that that uniform was in use, unchanged, for a good thirty years, but -- citing the movies' "monster maroons" (at least 2278 to at least 2294, but as late as after 2311 per secondary sources) -- there would be precedent. My takeaway is more that, even with whatever temporal tweaking having those glimpses of
a future allows those witnessing them to make -- intentionally or un -- the general tone is that a change to that uniform and insignia sometime in the late-24th/early-25th century is "inevitable".
Tracking all this crap isn't that hard. I've been doing it for decades, with help up until a few years ago from James Dixon. Not bothering or not caring shows a lack of respect for the setting/universe/property.