This is what Guru Gobind Singh Ji Thinks about Shivji, brahma, ved and kiteb. See the importance he has given to his own guru in Sri Dasam granth sahib:
ਆਜ ਲਗੇ ਤਪੁ ਸਾਧਤ ਹੈ ਸ਼ਿਵ ਊ ਬ੍ਰਹਮਾ ਕਛੁ ਪਾਰ ਨ ਪਾਯੋ ॥ ਬੇਦ ਕਤੇਬ ਨ ਭੇਦ ਲਖਯੋ ਜਿਹ ਸੋਊ ਗੁਰੂ ਗੁਰ ਮੋਹਿ ਬਤਾਯੋ ॥੧੭॥
And for knowing whose Mystery, Shiva and Brahma are performing austerities even till today, but could not know His end; He is such a Guru, whose Mystery could not be comprehended also by Vedas and Katebs and my Guru has told me the same thing.17
ਆਜ ਲਗੇ ਤਪੁ ਸਾਧਤ ਹੈ ਸ਼ਿਵ ਊ ਬ੍ਰਹਮਾ ਕਛੁ ਪਾਰ ਨ ਪਾਯੋ ॥ ਬੇਦ ਕਤੇਬ ਨ ਭੇਦ ਲਖਯੋ ਜਿਹ ਸੋਊ ਗੁਰੂ ਗੁਰ ਮੋਹਿ ਬਤਾਯੋ ॥੧੭॥
And for knowing whose Mystery, Shiva and Brahma are performing austerities even till today, but could not know His end; He is such a Guru, whose Mystery could not be comprehended also by Vedas and Katebs and my Guru has told me the same thing.17
