Think of it this way , you only lose your souls if you die twice without picking it up , so if you got the a certain place once , the you shouls technically be able to get there a second time . Also , dying is also grinding for exp , allow me to explain , you got from point A to point B ( not boss ) , picked up 5000 souls , then die . When you get to point B a second time , well you get back the 5000 souls from before + the 5000 souls from currently runing through point A and B again . Here you have to decide if you prefer to continue or turn back to save your souls.
Also a bonfire behind every white door would mean unlimited boss retries with no consequence , the game is all about consequence , but despite this there are shortcuts to bonfires close to bosses most of the time , if you are patient ( or lucky)enough to find them . Rewarding a player for patience and perception.
Also there is a new game+ which makes the game even harder for more hardcore players . The game was made like this , to make players feel rewarded for their perserverance , ever time i beat a boss i highfive my gf because i feel so awsome . There is nothing wrong with the game , just the players. Being cocky or overconfident will get you killed . Being patient and cautious is often the difference between life or death. Best advice i can give is be observant , watch your surrounding , watch your enemies , watch you health bar , watch your stamina . Doing this will minimize your deaths in the world ( not boss fights). For boss fights , expect to die , the first time you fight any boss observe his movements, his attacks , his tells, try to predict his moves . How does he attack when you are close , when you are far , what can you block , what can you dodge.
Appart from that spend you souls ever chance you get unless you intend to buy a specific item soon. Souls are never ending , no need to save them up unless you planing to buy an item or peice if equipment right away . There is no shame in runing back to a bondfire because you have a lot of souls .
And lastly upgrand your equipment , try new weapons , new fighting styles , find a weapon your comfortable with and upgrade it .
Hope this helps .