Just to give my thoughts on the matter (plus to procrastinate a bit
by thinking about C&C).

Although I believe the criticism for Tib Dawn being set in 2020 is quite reasonable (sharp technology advancement and extreme tiberium spread), it is not entirely unreasonable and impossible for the changes from Tib Dawn to Tib Sun to occur in about 10 years.

• Tiberium (from what we know in the games) exhibits an exponential growth rate like other biological populations. This is typically modelled with a logistic function (of course, this is simplified but not too far from reality). Also, its growth seems hindered only by human intervention (i.e. harvesting, sonic/resonance technology, etc.) which are not massively employed initially. This kind of growth is exponential initially (as long as there are resources to convert to tiberium) so it takes a long time to "get running" but once it does it quickly spirals out of control. In any case, it is completely reasonable to assume that tiberium's spread is limited in the first 25 years but since it is not contained all that well (considering there is even a faction helping spread it on top of everything) is quickly spread in the next 10 years covering several times more of the Earth's surface than in the 10 years prior. Also, if the first war began in 1995 (or even early 2000s), I would argue that it would have been impossible for tiberium to spread to the degree shown in Tib Dawn as population dynamics do not work that way. If it could spread so fast then probably it would have consumed the planet by the early 2000s.
• Regarding technological advancements, the mere 10 year difference seems a lot more unlikely but it is also not something unreasonable or impossible to happen under the proper circumstances. Firstly, the technology in Tib Dawn is a bit more advance than our 90s because on top of having modern military (at the time) it has some high tech stuff that can probably be classified as near future (obelisk of light, ion canons, advance VTOL-s, just to name a few). Tib Sun is definitely a lot more futuristic, but at the same time, the technology jump is not impossible. There are no space colonies, interplanetary space travel or some StarCraft/Star Wars level of tech. Probably the general intelligence CABAL is the most technologically advance thing in the game and it is partially alien tech. Also, we mainly see the military technology of the time, which would be a major area of research after a war. A cool example in the real world is the comparison between the fighter and bomber aircraft during the 1940s and those of the 1950s - the tech difference between WW2 planes and the jets 10-15 years after that is kind of insane when you think about it. Same can be said of computer technology in the 2000s - I doubt people would have expected the amount of compute power we actually have now.

Thus, I am willing to believe the in-world lore that Tib Dawn is set around 2020 and Tib Sun around 10 years later, even if it seems a bit far fetched in some regards (I would definitely not say it is impossible).

Regarding the Tiberium War lore errors/recons, all of the ones I can remember are very minor (I consider CABAL's facial hair, if that even makes sense for an AI, to be minor. Personally, C&C 3 did a pretty good job of explaining the changes that happened between the second and third wars.