The Buddha criticized those who put their faith in scripture calling them the blind led by the blind. He proved that generations of people believing in scripture cannot prove the contents of the scripture. This answer provides more details.
He also debunked oral transmission of scripture in MN 95. It is no use blindly transmitting scripture for which the truth is unverifiable.
Suppose there was a queue of blind men, each holding the one in front:
the first one does not see, the middle one does not see, and the last
one does not see. In the same way, it seems to me that the brahmins’
statement turns out to be comparable to a queue of blind men: the
first one does not see, the middle one does not see, and the last one
does not see. Their statement turns out to be a joke — mere words,
void and hollow.
DN 13
He recommended to verify teachings using experience:
"So, as I said, Kalamas: 'Don't go by reports, by legends, by
traditions, by scripture, by logical conjecture, by inference, by
analogies, by agreement through pondering views, by probability, or by
the thought, "This contemplative is our teacher." When you know for
yourselves that, "These qualities are unskillful; these qualities are
blameworthy; these qualities are criticized by the wise; these
qualities, when adopted & carried out, lead to harm & to suffering" —
then you should abandon them.' Thus was it said. And in reference to
this was it said.
"Now, Kalamas, don't go by reports, by legends, by traditions, by
scripture, by logical conjecture, by inference, by analogies, by
agreement through pondering views, by probability, or by the thought,
'This contemplative is our teacher.' When you know for yourselves
that, 'These qualities are skillful; these qualities are blameless;
these qualities are praised by the wise; these qualities, when adopted
& carried out, lead to welfare & to happiness' — then you should enter
& remain in them.
Kalama Sutta (AN 3.65)
It's worth mentioning that there are concepts of faith follower and Dhamma (the teachings) follower.
A faith follower is not a blind faith follower and faith is not the end in its self. Faith in the Buddha drives a faith follower to move forward, but eventually, he needs to verify through experience too.
A Dhamma follower follows the teachings after having reflected on it. He too needs to verify through experience.
“What kind of person is a Dhamma-follower? Here some person does not
contact with the body and abide in those liberations that are peaceful
and immaterial, transcending forms, and his taints are not yet
destroyed by his seeing with wisdom, but those teachings proclaimed by
the Tathāgata are accepted by him after reflecting on them
sufficiently with wisdom. Furthermore, he has these qualities: the
faith faculty, the energy faculty, the mindfulness faculty, the
concentration faculty, and the wisdom faculty. This kind of person is
called a Dhamma-follower. I say of such a bhikkhu that he still has
work to do with diligence. Why is that? Because when that venerable
one…into homelessness. Seeing this fruit of diligence for such a
bhikkhu, I say that he still has work to do with diligence.
“What kind of person is a faith-follower? Here some person does not
contact with the body and abide in those liberations that are peaceful
and immaterial, transcending forms, and his taints are not yet
destroyed by his seeing with wisdom, yet he has sufficient faith in
and love for the Tathāgata. Furthermore, he has these qualities: the
faith faculty, the energy faculty, the mindfulness faculty, the
concentration faculty, and the wisdom faculty. This kind of person is
called a faith-follower. I say of such a bhikkhu that he still has
work to do with diligence. Why is that? Because when that venerable
one makes use of suitable resting places and associates with good
friends and nurtures his spiritual faculties, he may by realising for
himself with direct knowledge here and now enter upon and abide in
that supreme goal of the holy life for the sake of which clansmen
rightly go forth from the home life into homelessness. Seeing this
fruit of diligence for such a bhikkhu, I say that he still has work to
do with diligence.
MN 70
What about heaven, hell, gods, demons, rebirth etc? How do you verify those through experience? Do you need scripture or a teacher for those?
Well, read about rebirth and karma in this answer.
You will find that some of these unproveable elements serve as skillful means to solve mindset problems in the interim, while leading towards permanent liberation. It has a soteriological purpose.
Ultimately, the goal of the Buddha is permanent liberation from suffering (mental discontent).
Whether there is a real heaven or hell or gods or demons, or whether there are multiverses, or whether the universe is a hologram or whether subatomic particles are composed of superstrings, are all not important to the ultimate goal of Buddhism.
"Conjecture about [the origin, etc., of] the world is an
unconjecturable that is not to be conjectured about, that would bring
madness & vexation to anyone who conjectured about it.
AN 4.77
The parable of the poisoned arrow tells us that we don't need to know all the details of the poisoned arrow and its origin. This means metaphysical and ontological speculations are pointless. What's important is to remove the poisoned arrow as soon as possible. This means soteriological purpose and usefulness is all that is important.
"It's just as if a man were wounded with an arrow thickly smeared with
poison. His friends & companions, kinsmen & relatives would provide
him with a surgeon, and the man would say, 'I won't have this arrow
removed until I know whether the man who wounded me was a noble
warrior, a brahman, a merchant, or a worker.' He would say, 'I won't
have this arrow removed until I know the given name & clan name of the
man who wounded me... until I know whether he was tall, medium, or
short... until I know whether the shaft with which I was wounded was
that of a common arrow, a curved arrow, a barbed, a calf-toothed, or
an oleander arrow.' The man would die and those things would still
remain unknown to him.
MN 63
The Buddha's focus was empirical and soteriological, not ontological or metaphysical. The Buddha was only interested in what would end suffering (mental discontent) permanently.
In the past, as today, what I describe is
suffering and the cessation of suffering.
SN 22.86