After playing alot of hours with the newest DLC (and previously months ago with Machine Age too, a little with Cosmic Storms) I can share my personal experience and feelings about it. I only comment on the gameplay/content and not the price because prices and income varies.
Grand Archive:
While having less content then Machine Age, I enjoy every part of it. There isn't really anything negatively in terms of gameplay. There are basically two content branches in this DLC. The first is breeding space fauna and make use of it in various ways (e.g. using as fleet and/or just gathering for various boni). The second is finding various pieces specimen and displaying them in the eponymous grand archive.
In my opinion this is the best part about it because
a) It basically interacts with the base game and every other DLC as most/all DLCs add more specimen to collect. You can find them by simply interaction with the various game mechanics (e.g. anomalies, events, unique origins, civics, trading with AI, astral rifts, etc.
b) You can mix and match your collection depending on liking, boni, etc.
I really like this DLC. While it may not adds the most or change gameplay fundamentally, it simply adds content or content alternatives to the basegame with very good interaction with other DLC.
Cosmic Storms:
Honestly, I'm in the same boat like most of players and reviews (see Steam reviews...). In general, the raw idea of storms and interaction is a good idea. Visuals are nice. But the mechanic itself can be summarised by having a random factor that only/mostly adds frustrating temporary modifiers to your systems. Protection is costly (research, build slots) and I don't see the fun in it. To add insult to injury, obvious interaction with other DLCs were missed (Zroni Stormcaster). If you want to profit you have to take the origin and corresponding civic.
The best part about Cosmic Storms: You can disable everything via gamestart options. I did this and don't look back. In my personal ranking about every DLC this easily gets last place by a wide margin.
Machine Age:
One of the largest DLCs in terms of added content. It heavily centers arround cybernetic and synthetic ascension by adding alternative government authorities to both of them, three new alternative and wastly different synthetic ascensions for machine empires. It adds individual machine empires and also a new crisis. This new crisis also has some interaction with other DLCs.
Due to the large content in terms of all the above plus new origins, civic and ascension traditions, there is alot of replayability, roleplay, things to try.
In my opinion there is nothing bad to say about the DLC itself, only that instead of a direct follow up DLC about Genetic/Psionics ascenion rework, they are left in the dust, basically unchanged. Due to the powercreep especially arround the machine ascensions, the genetic ascension feel really out of place (In comparison, even if they differed in power before this DLC too, it wasn't that extreme of a discrepancy both in power and diversity). Earliest we get something will be next year.
Other then that it somewhere at the top 1/4 of all DLCs in terms of enjoyment and amount of content.
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TL;DR:
Machine Age and Grand Archive are worth it.
Cosmic Storms isn't worth it however you won't reduce your enjoyment because you can simply disable everything via options before gamestart.
Therefore to keep it simply, if you don't think Season 08 pass is too pricey for you, you can simply grab it (fire & forgot). Alternatively either go for Machine Age for huge content based arround Cybernetic/Synthetic ascension and/or Grand Archive, which simply adds stuff, especially if you already own alot DLC.
Really appreciate this post, thank you
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