From memory, problems that existed in 1.9 where:
• Sectors - the automation and AI of sectors was largely seen to be lacklustre. It didn't upgrade things, most of it didn't work very well, and there were numerous threads asking the devs to look at improving the sector AI (I'm certain that sectors were the first quarantine thread). Now planetary automation does upgrade and build things, but it's incredibly capricious in its decisions on what to build, and there doesn't seem to be any logic to some decisions, such as building housing buildings on planets with no jobs, or vice versa.
• Doomstacks - £Fleet combat and warfare in general before the overhaul was basically 'who has the biggest fleet and who won the first engagement'. If you won the first engagement (usually by having the bigger fleet), you won entirely. The opposing empire would not be able to recover from the defeat and you would have impunity to take their territory as you saw fit. While doomstacks are not 'fixed' in subsequent patches since 2.0, the change in the warscore system does give losing sides opportunity to ally itself with others for protection. The AI however is still in a bad place and needs refining to get it working well.
• Mineral Monopoly and economic snowballing - Minerals basically were the economy; if you had a strong supply of minerals you basically won the game. However given that the other resources were food and energy, it was much much easier to acquire minerals, further adding to the 'boring' state of gameplay. The newer system in theory promised to make the economy more complex and provide some decision making on what to focus your economy on. In practice it mostly changed the meta from minerals to alloys and added some more steps to get to the same point (with the addition of creating death spirals for some AI unable to acquire as much territory)
• General lack of things to do - Taking the above into consideration, there really wasn't a great deal to the game in 1.9 other than 'get as many minerals as you can, build the biggest fleet and win'. Arguably this is still true of now, albeit with an economic system to tweak and now the Galactic Community to try and influence others and while some may say these have not been implemented well, they at least exist, where before there was literally one thing to do (ie swing the biggest space member in the galaxy).
There were other things as well but these largely got scaled back or are still bugged out now
Yep.
They fixed sectors by removing any point in using them or any flavour from having them lol.
no space-autobuild
pre-utopia, factions were tied to sectors and pushed for autonomy/independence etc.
Moreso if you had pissed off alien pops (they'd want to reform their old empire), slaves might try and make their own liberated nation from a sector etc.
Doomstacks are still alive and kicking.
A lack of hard-counters (e.g. AOE weapons melting multiple ships clumped up) and an AI that never specialises its fleets &
A warscore system that generally prioritises ... basically "K/D ratios" over actually capturing and holding various bits of alien infrastructure or systems
will always mean large blobs of "generic"-build ships swarming the enemy are the best strategy.
Mineral economy was replaced with alloy economy.
Until they add legit non-mil ways to play like culture/religious warfare a la civ etc, this will always be the case.
General lack of things to do in midgame still.
Pop micro doesn't count,
Archaeology, which should be dig-sites popping up in your empire in the mid-game, appears in the earlygame for some reason unknown to me.
Inter-empire diplomacy remains too shallow to meaningfully add to gameplay ("Set envoys and forget", "set GC votes and forget")
and fails to offer a "non-war" way to play.
People keep asking for "unifying federations" we... actually had that. Sort of. And we could have had it again via federations. PDX missed a huge opportunity.
Pre 2.0 sectors could be made largely autonomous, doing their own stuff without player input.
A federation could have a "final form" whereby it becomes 1 nation with each old nation being a sector under a new flag (the player always becomes leader in SP, could have co-running in MP, or just disable it in MP if thats impossible, but i think the clausewitz engine supports 2+ players on 1 empire as its doable in HOI4)