The Bluether story is based on the premise that Uther's soul is split into two parts (which isn't problematic in and of itself since we had the same thing with Alexandros' soul shard) but then only incorporates the experiences and character development of one part into the actual story, effectively erasing everything that happened to him between WC3 and Shadowlands.
Uther throwing Arthas into the Maw also hardly constitutes character development since it's basically just what Uther would have done in WC3 if he had the power to do so. So, in a way this is the same "factory reset" you criticize when it comes to characters like Jaina. It's doesn't build character - it's regression. I also disagree with the notion that Uther's ghost could have been just as easily replaced by Terenas without having any impact at all. While Terenas was his father, we hardly see his relationship with Arthas portrayed in the original WC3 story whereas Uther is his mentor and functions as an actual father figure. The real conflict and emotional impact when it comes to Arthas' betrayal always stemmed from his relationship with Uther. Terenas didn't even live to see Lordaeron destroyed whereas Uther was pretty much there the entire time before ultimately dying to his pupil. So, no it wouldn't have been the same thing.
And this isn't even taking into account that they completely purged the whole 'Light' part from Uther the Lightbringer which is boring and lazy at best and cynical and nihilistic at worst.