Nerf Ottoman Government, the monarch stats railroad it into a dominant position in every game
The game can take quite strange turns with their rulers. I'd say 90% of the time they have crazy good rulers with max - or close to - monarch points. If Mehmed lives a long time they generally get a sweet run and are dripping in monarch points from the start of the game due to their government type. If Mehmed dies early they can go the other way and get average or even bad rulers.
Generally playing in their region or sphere of influence tends to make them stronger. Playing as a minor in the Caucasus I've never seen the Ottomans fail, but playing as a minor in Ireland I have seen them fail several times. I've also notice the Mamluks are so bad now there's no point allying them. I did a run a couple of weeks ago, was allied to the Mamluks, who joined a defensive war when Ottos attacked their other ally. This was about 1475. Mamluks had same tech level and more troops but didn't even fight one battle. As their ally I could see their troop movements and they basically sent their armies down to Yemen and let the Ottomans roll through their lands, eventually submitting and losing the lands of the levant. Suffice to say I ended the alliance.
Another experience. I was playing a Caucasus minor. Year was before 1500, Ottomans attacked Albania, which must have joined the HRE as Austria called to war with their junior partner Hungary. Their ally Castile joined with their junior partners Aragon and Naples as well as Venice and Genoa who were allied to Albania. I was like sweet, no way the Ottos will win this war. Albania alliance troop numbers were 3:1 and still they lost. This example is probably more an AI issue but still , how did the Ottos not lose that war...
Making the Ottomans weak isn't the answer, but as many have said in the numerous threads regarding the Ottomans there needs to be some balance changes because playing against them is not a fun experience when they have 100,000 troops by year 1500 and second most powerful nation has half that number. It's also not realistic their stability should constantly sit at +3.