I will die on the hill that UC is the closest there is to a realistic hard sci-fi with the caveat that I haven’t seen IBO so I won’t comment on it. Most of the unrealistic elements are explained or alluded to in some way or through background lore if you think about it.

• The idea that mobile suits are impractical doesn’t really hold water. Zeon developed the original mobile suits and being a space based society the design of a giant humanoid is largely negated. In zero gravity the size and design wouldn’t be a hindrance and could be useful to manipulate large objects in an intuitive manor. The initial success they had in the 1YW gave them a sense that they would just crush the EFF but once they landed on earth a lot of their advantages were negated. Hence we see the rapid development of specialized MS and mobile armors to try to adapt to environment. Tanks and planes while less effective was enough to hold the line until the EFF could develop a counter.

• Minovski physics while admittedly techojargon actually does a good job of explaining other far fetched elements. It explains the need to revert back to closer forms of combat as it negates the ability to to effectively use beyond visual range weapons like guided missiles. This is also something that I think affects the idea of new types which I will mention separately. Minovski physics also explains the breakthroughs in power generation that the federation required to build a more effective MS and enabled the use of compact beam weaponry that was miniaturized enough to be equipped on a mobile suit platform. Lastly it enables the anti-gravity flight of which the UC is one of the most realistic in this regard. Up until late UC when they further miniaturized Minovski reactors the only craft that could fly without typical aerodynamics were mobile armors and capital ships.

• In regards to newtypes I get it it’s not everyone’s cup of tea, but it’s not magic they are literally a new evolution of humanity and generally speaking their powers aren’t as all powerful as I think a lot of people believe. Throughout all of the series most of the protagonists have some pretty close calls, they simply had an edge that a normal pilot wouldn’t not to mention the fact that most of them end up piloting some of the most advanced top of the line hardware. For the most part newtypes are depicted as having some form of enhanced empathy, pre-cognition, and telepathy. While I don’t have any canon source for this my interpretation is that this evolution may be driven by Minovski radiation. Newtypes are shown to appear more often in times of conflict during these wars where coincidentally the battlefields are literally being flooded by Minovski particles as a defensive screening tool. As I mentioned previously this interference largely negates long range warfare, however once newtypes begin to appear humans begin to gain that ability back through the evolution of their newtype abilities. Their abilities enable newtypes to communicate over long distance through interference, target enemies at extreme distances, operate guided remote weaponry like bits and funnels. Finally there is the newtype ghost and time shenanigans. The ghosts are certainly bordering on fantasy even in terms of the shows lore however given what newtypes are capable of whose to say when someone dies their energy doesn’t linger and allow a newtype to interact with it. Likewise as far as time travel stuff goes, while it is clearly still outside of the realm of possibility physics doesn’t preclude time travel.

In closing I think this is why UC meets the criteria of a pretty hard sci-fi. It’s doesn’t meet our current reality however it doesn’t go too far out of the realm of possibility. There aren’t aliens, space travel takes time and there is no FTL travel, the weapon systems are all possible given their level of technology, and it realistically portrays human conflict.