Constantly increasing a system's complexity inevitably results in a number of variables and interrelationships that, in this particular case, haven't been fully captured yet.
Leaving aside that your sentence isn't fully legible, what makes you think Segwit complicates the system?
It's a simple change: today, blocks contain transactions and signatures. After Segwit, the signatures can be put into a separate, parallel block structure.
If you're having problems with understanding that, Bitcoin isn't for you right now. You'll just have to wait until people that are capable of understanding these simplicities have established your faith in the change.