My own takes on the eras go like this:
(Just for fun): Pre-Age of War: Shouldn't you be playing
Team Yankee instead if you're interested in the Second Soviet Civil War?
Age of War: Just kind of "there", and much of it was BattleTech without the BattleMechs, meaning the most unique thing about the setting isn't even present. It is interesting from a "how we got here" standpoint to be sure.
Star League: OK, but not my complete favorite. Lots of skullduggery and the SLDF keeping its thumb on things so that open war rarely broke out. It just seems bland and staid, but then I haven't read much fiction set in the era, just the sourcebooks, so there was probably much more going on under the surface than just the three Hidden Wars.
First Succession War (breaking the three SW into their own eras as they're different enough): Thematically interesting, but often extremely dark, almost approaching Jihad levels of dark. Then again, being that this was the war that gave us the Kentares Massacre, the terminal decline and death of scores of inhabited worlds and the widespread use of WMDs, it can't help but be. But it seems better served as a prelude into the later wars.
Second Succession War: Better, and has some real crunchy lore stuff to it such as the ComStar War, the rise of Conrad Toyama and the conversion of ComStar from "Ma Bell with an army and navy" into the be-toga'ed schemers we all know and love, and the saga of Jinjiro's death.
Third Succession War: My favorite era. I love the "throw
Mad Max, The Prisoner of Zenda, Dune,, the Old West, World Wars One and Two,
The Seven Samurai, and modern '80s history and style into a blender and drink the awesome smoothie that comes out" aesthetic. The fact that it is a 150+ year-long war gives a massive canvas for wargamers to create their own battles and engagements, and the decline of civilization gives some great story opportunities for roleplay.
Fourth Succession War: Hanse's great curbstomp. Interesting for shaking up the status quo, but the creation of the largest contiguous territory since the Star League just seems bland, and set the stage for the stuff that came later. The post-3030 wars also don't grab me all that much, with the Andurien seccession and invasion of the Capellans being "Humphries gotta do Humphries" again (and I would have preferred them succeeding, not because I'm any sort of Andurien fan -- as a Marik player, those rebellious little shits have been more trouble than they're worth and probably should have been deposed by someone else long ago, but because seeing another wholly new interstellar power emerge would have been a truly interesting development. Fair enough, we did get the FRR for all of 30 seconds, I don't count the SIC as they were more a protectorate of the FC and weren't of much consequence in the greater scheme of things) and 3039 was just "Hey, Hanse, look at the shiny new toys we got from ComStar".
The Clan Invasion: In this era, the Clans were just BEMs in a universe without BEMs and the tech disparity attracted munchkins. I am not a fan of this era, honestly. It does have a few good lore points, such as getting the Successor Lords to play nice with one another for once (I especially love how Hanse was able to assist Takashi and yet still keep his promise of "no FedCom troops crossing the border for the duration"), and the deconstruction of Hanse Davion's "magnificent bastard" tendencies when Victor tries to pull the same antics Hanse did flawlessly with only one problem -- him not being Hanse. But for the most part I'm not enamored of this era.
FCCW: Just never interested me. It seemed like it was a "we have to stir the pot because wargame" era more than anything. Also this era debuted the "Project Phoenix" attempt at redesigning the Unseen, and these were
fugly for the most part.
Jihad: I hated Tommy Marik's omnicidal roadshow. It to me just ended up being "too bleak, stopped caring". Not to mention, it seemed a bit out of character for the be-toga'ed schemers to just go full temper tantrum. Why not just subtly overthrow/replace the rest of the Successor lords like they did Tommy? As an FWL player, I also was both upset and amused by the breakup of the FWL -- upset because they are my faction, but amused because it seemed just so in character for the FWL to be the first to balkanize.
Dark Age: The hot mess that WizKids left in Catalyst's lap. Fair play to CGL they tried their best to shoehorn in the lore from
MechWarrior: Dark Age, but it just left me cold. Also no FWL, no sale.
IlClan: This is the return to form that BattleTech needed. Getting out from under the shadow of the past few eras, better integrating the Clans into the setting as something other than an outside invader (Rasalhague Dominion, Raven Alliance, and the Sea Foxes on their way to becoming the new ComStar), and giving the Sphere an interesting new threat in the form of Alaric's Wolf Empire and IlClanship. And the FWL is back, baby! The idea of making the Periphery powers actually relevant (although in fairness, this was a thing as far back as the later Clan Invasion/FCCW eras with the Trinity Alliance) as interstellar powers also opens up whole new avenues for Heavy Metal Mayhem and makes the Canopians, Taurians and those Roman fanboy hosers appealing as factions. This is my second-favorite era after the OG Succession Wars.