If at all possible, you need to move out. By staying you are enabling your parents to keep their unhealthy lifestyle. If need be, contact Adult Services where you live. If the house is a fire hazard, the authorities will provide a certain degree of help, probably a referral, to an expert on hoarding and junk removal. You will not convert them by remaining there. If you’re unable to live entirely on your own, there are services available to you for reduced rent, wellness check-ups, food services, jobs you are capable of doing that make allowances for those with mental illness. I’ve a cousin who moved out of a similar situation. The house was so cluttered with stuff that he fell down the stairs and broke his leg, requiring surgery. He could not be released to return to a hazardous living condition. Since 2008 he has lived with a two other men in an apartment funded by City Wellness of Cleveland. Each man is expected to do his share of common area chores, ie, cleaning of kitchen, sitting room, restroom. Each pays a share of rent. Two of the three work. A social worker stops in once every week to make sure things are running smoothly. My cousin works part-time for Goodwill Industries and sidelines by designing web sites from home. He earned his GED and is presently taking on-line classes towards accounting. His mental issues are vastly improved since moving out. His Dad, my uncle passed away in 2014, and his Mom has moved to a senior apartment complex. His two sisters come regularly to keep her hoarding under control. It is also helpful to know that hoarding will result in eviction. She’s become able to monitor herself for the most part. My cousin is not a hoarder although he was at first thought to be one. If anything, he’s a bit too much a minimalist.
There are things you can do to help your parents. I think you’re right about a person’s home being a reflection of the soul. It’s not your fault your parents don’t tidy up. Do yourself and them a favor by moving out.