The Season of Shattering was the first season I was fully around for as a moth, and when I look back on it, my feelings are mostly summed up with "it was okay". My opinion may be influenced by the fact I was mostly a moth at the time, so I wasn't as into the lore as I am now. The in-season experience left a lot to be desired considering it involved the same kind of quest every. Single. Time. I think during SoS I only did the shard events when I absolutely had to just to keep myself from being tired of clearing shards.
With regards to the spirits (or lack thereof): For SoS in particular, I actually kinda like their non-humanoid forms. To me, it gives me the impression that these "spirits" are beings or abstract concepts that existed before the players, and even before the other ancestors. (It doesn't quite explain why these ancient concepts are offering me cool hats and props, but that's something I'm willing to ignore as a part of the game that doesn't translate well to stories/lore.) That being said, this is a concept I'd only allow for SoS or seasons with a similar concept because the non-spirit forms does bring up the question "How will these return as TS, if at all?" Other seasons that use non-spirit forms include Revival and Nesting, and I am very unsure of how those seasonal items will come back, if at all.
On the lore: Looking at what lore can be gleaned purely from the Shattering memories, I would agree that it leaves more to be desired. The only memory that has something I could chew on is the one with the Eden crystal and all the Elders. Other memories have things to think about, but that's only if you have some additional info about the game's lore which may not be obvious to all players. Speaking of which, there WAS additional lore during Season of Shattering, but these were spread as poems posted to social media by official TGC accounts. Some of these poems give additional context to the Shattering memories, and the best example of this is the manta memory (maybe the jellyfish memory too but the poems are a lil' samey).
The manta memory depicts a swam of mantas, which doesn't seem too special until you pair it with the associated poem posted on social medias:
Soft wings flowing to bright beacons
Drawn from the path, trusting until too late
Bound in a merciless harness
Soft wings despairing against stone
I'll leave how this could be interpreted up to any reader, but doesn't that give you more to chew? This is why I'm not fully on the boat of saying the lore of Shattering was not there, however this also doesn't really fix things. Because these poems were only posted to social media and not shared in-game (to my knowledge) they are bound to be either looked over by players who don't have an account on X, Y or Z, but they are also bound to be swept away by other posts. These poems were posted two years ago, how can a new player be expected to find/know about them? There's also an additional problem where because these weren't spread in-game, that these poems actually have zero bearing whatsoever.
In retrospect, the Season of Shattering seems like one of those seasons that's better enjoyed as a new player -- and one that wasn't around for the Season. Like, the way you access Shattering now is probably less direct than all other seasons, so I think that'd create a sense of intrigue that motivates players in a way the season couldn't. Participating out of season also means players can do the next quest immediately or at least the next day when there's a shard, instead of having to wait like, a week to do the same thing anyways.