Outside of the laborious and grindy mechanics and strange focus on upgrades and minmaxxing numbers, as well as the gacha-esque evolution of the trooper card mechanic, Ishin is a story so gorged with fanservice and series tropes that's able to temporary blind the player long enough that they don't realize Real People and Events are being talked about and boiled down into RGG's tried and true character archetypes. Kiryu in his unwavering determination and stubbornness to stand behind his ideals doesn't gel well with a complex and nuanced historical figure like Sakamoto Ryoma and his very limited emotional palette throughout the story is disappointing. As a whole, Ishin shares the heart of the rest of the franchise, but is bogged down so much by its willingness to play it safe with storytelling and indulge in constant roadstops.
The remake's issues have been explored thoroughly compared to the original experience, but I still feel a lot of the fundamental flaws and issues with Ishin aren't new.
...At the same time, the entire ending sequence is some of the most earth-shattering kino this franchise has ever seen. They managed to step things up and top Aizawa's QTEs in Yakuza 5. It ties the otherwise inconsistent and iffy experience in a really nice bow and always leaves me with my heart pounding.