
Albert Einstein, and Erwin Schrödinger, two of the founding fathers.
These men were bold enough to call for an alternative theoretical construction which
would empirically agree with quantum theory, yet which would restore completeness and objectivity to
our description of nature.
Einstein, in a letter to Schrödinger:
"You are the only person with whom I am actually willing to come to terms. Almost all
the other fellows do not look from the facts to the theory but from the theory to the facts;
they cannot extricate themselves from a once accepted conceptual net, but only flop about
in it in a grotesque way."
Einstein on quantum theory:

(From his answer to Heisenberg's defense of orthodoxy (see Dialogue
between Einstein and Heisenberg ) )
"...every theory
in fact contains unobservable quantities. The principle of employing only observable quantities
simply cannot be consistently carried out."

"What does not satisfy me, from the standpoint of principle, is (quantum theory's)
attitude toward that which appears to be the programmatic aim of all
physics: the complete description of any (individual) real situation (as it
supposedly exists irrespective of any act of observation or substantiation)"
Schrödinger on quantum theory:

"If we have to go on with these damned quantum jumps, then I'm sorry
that I ever got involved."

"Let me say at the outset, that in this discourse, I am opposing not a few special statements
of quantum mechanics held today, I am opposing as it were the whole of it, I am opposing its
basic views...
... it would seem that, according to the quantum theorist, nature is prevented from
rapid jellification only by our perceiving or observing it. And I wonder that he is
not afraid, when he puts a tenpound note [his wrist watch] into his drawer in the
evening, he might find it dissolved in the morning, because he has not kept watching
it."

Max Planck, one of the most important of the founding fathers, it was he who first formulated the quantum idea in terms of the radiant energy given off by a heated body ( think of the heated metal in a blacksmith shop or a stovetop. ) Planck was deeply dissatisfied with the quantum theory eventually constructed and accepted by the mainstream.
Planck on Copenhagen [ accepted ] quantum theory:

"
"It is true that we must reject as meaningless the hope that it might eventually prove possible indefinitely to reduce the inaccuracy of physical measurements by improving the instrument. Yet the existence of an objective limit like Planck's quantum is a sure indication that a certain novel law is at work which has certainly nothing to do with statistics. Like Planck's quantum every other elementary constant, e.g., the charge or mass of an electron, is a definite real magnitude; and it seems wholly adsurd to attribute a certain fundamental inexactitude to these universal constants, as those who deny causality would have to do if they wish to remain consistent."

John Stewart Bell, who elaborated the concerns of Einstein and
Schrödinger more clearly than anyone, via his championing the cause of
hidden variables, and in particular de Broglie and Bohm's hidden
variables.

(A statement appearing to support Einstein's remarks in Dialogue between Einstein and Heisenberg)
"But to admit things not visible to the gross creatures that we are is,
in my opinion, to show a decent humility, and not just a lamentable addiction
to metaphysics."

"The usual nomenclature, `hidden variables' is most unfortunate. Pragmatically minded people can well ask `why bother about hidden variables that have no effect on anything?' Of course, every time a scintillation occurs on screen, every time an observation yields one thing rather than another, the value of a hidden variable is revealed. Perhaps uncontrolled variable would have been better, for these variables, by hypothesis, for the time being, cannot be manipulated by us."

"The 'Problem' then, is this: how exactly is the world to be divided into speakable
apparatus...that we can talk about...and unspeakable quantum system that we cannot
talk about? How many electrons, or atoms, or molecules, make an `apparatus'? The mathematics of
the ordinary theory requires such a division, but says nothing about how it is to be made...
...Should not fundamental theory permit exact mathematical formulation?
Now in my opinion... ...The quantum phenomena do not exclude a uniform description
of micro and macro worlds...system and apparatus. It is not essential to introduce
a vague division of the world of this kind. This was indicated already by de Broglie in 1926,
when he answered the conumdrum
wave or particle?
by
wave and particle.
By the time this was fully clarified by Bohm in 1952, few theoretical physicists wanted to
hear about it. The orthodox line seemed fully justified by practical success. Even now the
de BroglieBohm picture is generally ignored, and not taught to students. I think this is a
great loss. For that picture exercises the mind in a very salutary way."

"Why is the pilot wave picture [de Broglie and Bohm's hidden variables] ignored in text
books? Should it not be taught, not as the only way, but as an
antidote to the prevailing complacency? To show that
vagueness, subjectivity, and indeterminism are not forced upon us by
experimental facts, but by deliberate theoretical choice?"
