Or you can leave all your transfers to your DoF.
Or you can only sign players you deem to be 'realistic'.
Or you can restrict yourself to how many players you sign
Or you can only use scouts and not the player search or any other exploitative way to find players.
.....
Or you can sign who you want, when you want, and have a fun time. It's called choice and everyone has it.
The beauty of FM is its open-endedness. There's no gamey 'difficulty levels', there's no senseless restrictions for the sake of it other than what occurs naturally (transfer budget, wage budget, etc), but on top of that, there's tons of different ways you can play it. There's even countless mods out there that make the game harder, from skins that hide player attributes, to mods that ramp up injuries, and loads in between.
Now, this is not to say the game can't improve and become more naturally difficult, but as has been said countless times, the risk of doing that possibly outweighs the rewards. SI are a business after all. They actually do a great job in making sure the game caters for as many people as possible.