You should lower the difficulty if you don't want a challenge, seems to me you just want to easy stomp anything whenever you want at a chill pace. Lower difficulty suits you and that's one way to play
"Historically this", "Historically that", France doesn't take Pale and conquer GB Ireland and no CB this and that, the pope will not kiss your feet for getting the blue blob achievement. Brandenburg doesn't get Prussia until "MUCH MUCH" later and starts to gobble up little states. Sweden doesn't yeet Denmark on 11th December and the Byzantines are not long for this world. And let's be real, Burgundian inheritance is such a cheat that even if you started as a smaller nation and got the inheritance, it ruins your game totally because you just become so strong that you can beat anyone in the game, there's no point continuing the run unless you want to do a WC. Most mission tree that makes the game playable is ahistorical with "historical justification", when you play Ethiopia, you will yeet the Mamluks. Manchu will finish off the Ming with Y E A R S of margin, uniting Japan and invading Korea and actually win, YEARS earlier.
Everything a player does have huge impact on the game in more ways than what most people think. When you ally Austria but you don't help the AI in battle when they expect to be reinforced because you're next to them and they deem we have sufficient numbers, or help them siege forts, you're crippling them, that's one relationship slot they could've had. When you play an Elector and decided to ally all electors and cripple Austria from getting mission to union Bohemia, you're crippling them.
There's the RNG, which is what makes this game so great. It allows the game to be replayable, each run is different with each power having different rivals/allies. Some games, Austria gets Hungary peacefully, others through force. When they get Hungary, sometimes Poland took 4-5 provinces from HG already, sometimes ottoblob took 4-5 provinces, sometimes both. Sometimes none at all. Sometimes Austria inherits Hungary entire, others they lose the union and have to war again.
A strong Austria is a good buffer against ottoblob, so is the PLC, but sometimes PLC doesn't form, sometimes Lithuania doesn't even fall under a union. People just never consider what they're doing to the game when they're having fun expanding. When you're killing the PLC as Muscovy, you're making a dent. When the Catholics don't have a crusader modifier against the ottoblob, they're more likely to fall. It is entirely possible for a smaller/medium sized eastern catholic AI state to beat back the Ottomans just by having the crusader modifier with their allies.
The big nations have their own expansion path otto is just built to blob, they're not as good at colonizing. If you're too weak to crush the otto, try to find alternate way to expand your power, colonize (charter trade company and start fabricating claims.), dominate nodes and collect trade/funnel it back if you can make use of it, the ottos can't do thatas well as an EU power. Eventually they will be no match for you, the trade power scales so incredibly well that you can pretty much field huge forces and mercs. You should not expect yourself to beat the blob when your first ideas are what? Exploration, Expansion? Economics/Trade. If you want to fight early, you will need quantity and manage your points well and not dump all points in ideas and neglecting tech.
When you build an alliance block against the blob, you have to watch out for their troop movement instead of blindly sieging. If you intercept their troops at a friendly fort, you get defensive bonuses and makes the fighting "manageable". They siege quick, and our AI friends are so incredibly stupid. Even in the patch that famously make the AI build forts, Poland seems to rarely fort their capital and ever so inclined to peace out and leave you to die if their capital falls.
I think this is an issue in of itself, they rarely ever wait for you to unsiege their capital even if they have the manpower, economy and fielded troops ready to continue the war unless they have the religious war modifier which makes them less willing to peaceout.
I think it's mentioned already, even Mamluks are being very silly, a few provinces occupied and they will be willing to peaceout and handing out several provinces to the blob for no reason.
I find the Ottoblob to be on the right level of strength, it's rather the way the other AI play that is the problem, and to some extent the expectation the AI have of player and vice versa in what battle is winnable and how troop movements should be in a particular war. Ottoblob needs to be strong.. because we all feel sorry for him don't we, they have no friends. Anyone they ally usually disappear after a while, or is so weak and irrelevant and they rarely have more than 1 or 2 allies.
If sometimes you get contained and you feel stuck, just end the run. RNG is there to make every run interesting and somewhat unique. Sometimes you just have to do other stuff and chill while waiting to see an expansion path if you get contained by guarantees, alliance, etc. GP intervention is not unique to ottoblob btw, any great power will regularly try to intervene; the most annoying being Ruskij, Baguettié and Ottoblobbü as they are a massive land power with land connection in Europe. But that's the game for you, you can also intervene as well. Any power that gets weakened in manpower/troop number will get attacked, even you.. any size. And it makes sense, that's what most players do against AI as well, right?