in my games i havent hit a crisis yet since until the latest patch the lag made late game very tedious but i beat the khan off when he spawned on my border, i had about 20k fleet sat on a 10k bastion and just let him repeatedly suicide me until he died
every game so far i have had 6 100k fleets by 2400 playing on 600 star galaxy on grand admiral, once i get to that many ships i get a bit bored building them and just wait for the crisis
so i dont think there is any real problem with being able to field fleets to match the crisis, in fact i think it might actually be easier now to build big fleets at least in the end game. i remember struggling to get those numbers much more pre 2.2 than i do now, once i have a couple of ecumenopoli up and running the snowballing is ridiculous. i also think that whilst the cost to build ships hasnt changed the maintenance in alloys is much lower than it was in minerals so you dont lose your alloy income as your fleet grows as much as you used to lose mineral income. granted that might end up making sustaining a difficult war more tricky since you wont get the sudden huge boost to income you used to get after a costly battle but just building and maintaining massive fleets seems easy enough.
for those having difficulty a few things to consider:
pop growth is king in 2.2, use all means at your disposal to encourage more of it including but not limited to health care edict, high nutrition policy, encourage growth decision, gene clinics.
ecumenopoli are op, cool and fun as well but definitely op as all hell, always take the arcology ascension perk.
plan ahead, decide which planet(s) are going to be your ecumenopoli early and start developing their industry and city districts as soon as you can so they have good pop and are ready for conversion as soon as you get the arcology ascension perk, generally i find 2 to be enough to comfortably build and support 600k+ fleet power. once converted you can knock down the industry buildings as you build industry and forge arcologies. also knock down any industry you have built on other planets and resettle the newly unemployed specialists to the ecumenopolis. you want to make the biggest and emptiest planets your ecumenopoli, ideally size 25 but anything size 20plus will do at a push, since ecumenopoli lose all resource districts upon conversion try not to use mineral or food rich planets, doesnt matter so much for energy districts as ecumenopoli tend to end up with a butt load of clerks anyway.
when you convert to an ecumenopoli you will probably start with way too many housing arcologies and will want to convert some of them to industry or forge arcologies. if you find you need extra amenities on them at some point i prefer to build holo theatres or some other building that gives amenities rather than waste an arcology that could be producing alloys on a culture arcology. arcology slots are more important than building slots imho.
make sure you get a solid income of base materials before trying to expand your higher end industry too much.
fully exploit all the resource districts on the rest of your planets and dont put too many city districts on them until that is done, once it is done you can start building up city districts and filling up building slots until the planet is full. you will need 1 or 2 city districts earlyish to get the few buildings you do want on every planet and for some extra research centres since you dont really wanna build those on your ecumenopoli. if you are sitting pretty on resource income it can often be worthwhile leaving a couple of planets at low pop and resettling (if you can) excess pops to more important worlds that you are trying to develop quicker, like, you guessed it, an ecumenopolis or a research world.
dont build too many trading star bases, each one should have 6 trade hubs on it so they can collect everything within 6 jumps and they should be placed so that the fewest possible starbases will collect all the trade in your empire, most of the rest of your starbases should end up being anchorages. if you need more trade protection build naked corvettes for it as it is hull size not components that determine piracy suppression. also a bastion or 2 at key points with 6 hangar bays so they provide protection up to 6 jumps away can be helpful once your trade really kicks off.
merchants are great.
try to make sure that each of your borders is at a single lane choke point and put a fully upgraded bastion on it. bastions arent great, they arent gonna fend off a reasonable fleet on their own but if you park your fleet well behind the starbase and let the enemy engage your bastion first then move your fleet to support, your bastion will tank quite a lot of damage for your fleet which can save quite a few resources in ships that you dont lose. until i get gateways i tend to put a shipyard behind each such bastion and station a fleet at each shipyard. if you border a staunch ally or the xenophobe FE you dont need to fortify that border.
dont neglect your tech, there are a lot more key techs now than there used to be, in fact tech in general has become much more powerful and important than it used to be imho. in general i find it better to concentrate your tech on a few planets since it is much more efficient to build a few top tier research buildings than lots of lower tier ones. that said it can often be worth while when you have spare pop and nothing better to do with them to plonk down extra tier 1 research labs since they dont cost rare resources to maintain.
VERY IMPORTANT: dont build for the sake of it, you dont have to fill every building slot and certainly not as soon as it becomes available, doing so will just stifle your economy as you will be taking workers away from more important things and if you dont have enough workers to fill all your buildings and districts you are just wasting maintenance. always ask yourself if you really need that building before building it. it is far more important to maintain a healthy income on energy, minerals and food than it is to build just about anything else. its very easy to go on a building spree thinking your getting loads of cool stuff only to find your economy tank cos you run out of the basics as all your workers promote to more interesting but less useful jobs.
thats it for now, i hope this is helpful to some of you.
edit: oh yes, extra tech is never wasted, the end game repeatables are expensive and impactfull especially when stacked on each other, never stop improving your tech capacity.