Yeah it would have been nice to have another go at a ballot with big competition like vets, Ridley, K.Rool, Inkling etc. out of the way. Isaac would have definitely nabbed a better placing with how much the Ultimate speculation cycle has brought Isaac and Golden Sun more to the forefront (Rathalos tweet, fake leaks, assist backlash, Golden Sundays etc).
Only thing that seemed odd to me in the interview was the part where it says Sakurai doesn't follow internet reactions and doesn't know of fan predictions. Back during Cloud's reveal he even retweeted a mash up reaction that included notable YouTubers and Smash fans like Nairo, Etika, and HMK to name a few.
I also think him being Sakurai, creator of Smash Bros, that's it's almost impossible for him to not have some idea of what fans want. Even when it's not related to Smash, he gets bombarded with fan requests all the time. Of course he's likely not watching newcomer predictions for Smash type videos or know Reddits top 10, but he was aware that Ridley was an anticipated name for fans, even at the time of deciding to make him a stage hazard. He also talked about Geno's popularity and the want for a Final Fantasy character. So he does have some knowledge of what fans ask for.
I think Isaac is in a favorable position being brought back from Brawl. Aside from Gray Fox, he's the only other Brawl assist that made the jump. This keeps Isaac relevant for the next Smash a model to port/upgrade while also helping him to not fall into complete obscurity by skipping another Smash game. There's the usual stigma with being an assist but at the same time not having an assist or any prescence in Smash doesn't necessarily equate to a character having better chances to be playable either.
Ultinate's concept of World of Light and spirits also helped to shine some much needed light on the Golden Sun series. After everything the icing on the cake would be if we could get some kind of announcement at E3, a Definitive or Complete edition of Golden Sun. So many RPGs have been coming to the Switch lately, boy I wish Nintendo would take their own IP and do something with it lol.