It is done. I've assembled all 1297 Spirits, 100%'d World of Light, completed Classic and Century Smash with all characters, have all songs and all costumes, and have completed all Challenges, save for six that I didn't have enough Hammers for in Online.
My two biggest dissapointments-
1) The Milestones feel really slim compared to Smash 4. And no funny notifications like 'Show Me Your Moves!' or 'Your body is ready!'
2) Nary a single Captain N reference. C'mon, you've got Pit, Mega Man, and Simon all together again, but between every single Spirit battle in the game, every Challenge portrait, and each of their Classic end cards, we don't even get a shot of the three of them together. What gives?
All in all, I do have to say that Spirits and World of Light made for some spectacular single-player content, and Classic Mode was better than ever. Century Smash is still *** (I hate the Fighting Mii Team and I have since 4, it's too hard to distinguish them apart when there's so many and they're all randomized), but it's nowhere bad enough to be a negative mark against the game (I just wish they were the Fighting Alloys instead, or an Assist Trophy squad like a lot of people were predicting). Most frustrating Challenge to complete was killing a Lv 9 CPU with Robin's flurry attack.
And now that I've wrapped up basically any and all chances to obliterate CPUs with PK Freeze, I have no choice but to actually start learning characters other than Lucas again. Bowser Jr. feels somehow worse than Smash 4 but I still love him, and RIdley is strange to grasp but I like him. Simon/Richter and K. Rool are also pretty fun from the time I had with them in Classic. In a game with 76 (and counting!) characters, I'd be shocked if I didn't end up with at least 20 I thoroughly enjoy.
Kinda late on this topic, but Joker's reveal pretty much blows away everything we expected with 'Nintendo picking the DLC characters', and a lot of 'insider information' regarding what was surely known about the VGAs and/or the DLC characters. I think Nintendo is going to do a damn good job of picking characters that would just be awesome to have cross over, regardless if how much the fanbase may want them. Persona didn't even have that big of a push for Smash, but I've seen nearly universal love for Joker making it in. I'm doubtful for any first party DLC characters, and double doubtful of any Spirits (let alone Assists) being upgraded to characters.
Overall very pleased with the game's single-player content and extremely eager for the Plant, as well as more news on Joker, and whomst'd've else may be DLC.
Small aside, I've already been wondering what Joker's Classic Route may be, probably something along the lines of characters who have 'Personas', like Zelda calling on Phantoms, Rosalina with Luma, Duck Hunt with Gunmen, Peach/Daisy with Toad, Popo with Nana, and Olimar with Pikmin. (I only recently realized Joker is the closest I'll get to Jojo in Smash so now I'm DOUBLE excited for him)