Alright I've finished the game, bar stark mountain stuff, so I think I can give a fair view on the game. Keep in mind that I played the game on set mode and didn't use reviving items + minimum healing items in battle (only fair if I use some since trainers spam full restores like crazy).
My final team was Rhyperior, Scizor, Salamence, Skuntank, Breloom, Starmie. I also had a Torterra up until the third gym, and a Rotom up until the Galactic Cyrus.
In all honesty, I'm not sure what I think of the game. I certainly poured a lot of hours into it, but partially because of boredom. The early game was entirely unfair to Turtwig users, with the 2nd trainer having full restores, 4 Pokemon and a Beldum which fully walls Turtwig. The two ace trainers on route 215 with like 10-12 fully competitive Pokemon, in the rain, came out of nowhere, and although I like the concept, imo it was too early in the game to throw that (especially with the Raikou) and it's never touched on again (not even with the galactic multi-battle at Spear Pillar). The sailor in the Pastoria gym and the ace trainer in the Canalave gym (the ones that used to freeze the game) were inexcusable imo. Their surprise difficulty puts many other important trainer fights to shame, especially when they have cover legendaries, one of which is an essential part of the story's plot. This is the "12 year old on battle spot" mentality, where throwing legendaries at the player would seem to make the game more difficult. It does, but not in a good way. It sets the bar way too high when the game only reaches that level of consistent difficulty at the Elite Four.
Many important trainers don't even stick to their theme near the end of the game; Candice's highest level Pokemon was a Blastoise (though I did like that she was a doubles battle), Volkner had two electric types (Zapdos, Rotom appliances and Electivire are all viable...) but the Elite Four was ridiculous. Cynthia can have a pass even though her team is just semi-uninspired legend spam, since she doesn't have a theme in the original. But Aaron and Bertha don't have a SINGLE Bug or Ground type respectively between them. Hell, Bertha's lead is a Kyogre, the exact opposite of what her team is meant to be. There are plenty of viable Pokemon which fit the ground/sand team archetype. Flint had a sun team which is reasonable, but not nearly enough Pokemon to abuse the sun (iirc Moltres was on Lucien's team!). And because most of the psychic legendaries are wasted on other Elite Four members/Cynthia, Lucien's strongest Pokemon are a Giratina and a Darkrai, the opposite of psychic types. Galactic Cyrus got easier every time I fought him, to the point where I feel like if you just tweaked his original team members, it would have been more of a challenge. Also, the whole "no grinding is needed" thing is misleading. In my playthrough, I battled every trainer and generally fight a lot of wild Pokemon too just by travelling along routes, and I still spend several hours grinding on a few occasions.
There are positives though. Battles in the early/mid game felt difficult because they legitimately were. The galactic commanders, Fantina, Maylene all gave me a run for my money. The third rival fight and Wake even caused me to white out a couple of times (though I feel like that's partially because of additions this game makes, like Water/Dragon Milotic and Drizzle Politoed). Not sure if this is a good thing, but there are Pokemon at the start of the game which can make it a cakewalk. Speed Boost Blaziken, Water/Dragon Gyarados who finally has a powerful physical stab, all the psuedos in Wayward Cave, stuff like Scizor, Gengar, Togekiss, Alakazam (which I see above has Magic Guard)... although I haven't tried most of these Pokemon in a playthrough of this game, I can only imagine how much easier it would make it compared to my team. Though it was fun actually getting results with Pokemon like Skuntank and Rhyperior (Breloom felt like dead weight towards the end, partially due to no Spore). Scizor was 100% the team's MVP. In terms of whiteouts, I whited out like 4 times against the 2nd trainer with the Beldum, once more in Eterna Forest, twice to the Hearthome Barry fight, twice to the Ace Trainers doubles battle, twice to Crasher Wake, once to both the Sailor and the Ace Trainer that I mentioned above, once to Bertha and once to Cynthia. Think I reset against Fantina as well.
Sorry for the essay, but I've put a lot of time into this game and I hope you find my feedback useful.