First off I am a Hindu. I was born into one. I also love to eat a nice prime rib cooked medium rare (and a hamburger) once in a while. Now, do I fear that I would be excommunicated for eating beef? Nope. Cause there is no authority that can excommunicate me in the first place. I am very much a Hindu. I am free to believe what the Bhagwat Gita says or not believe a good portion of what the Gita says and I would still be a Hindu. I may even cherry pick what I want to believe from the Bible and the Koran. But does it mean there is no structure of any kind in Hinduism? Are Christians and Muslims Hindus?. Well! let me bring a different context (Political) and see if that would help explain.
Western concept of liberty as a political system: e.g. “Life, liberty and the pursuit of happiness”. It’s a very broad framework. It does not go into the minutia or stipulate what it is that would make you happy. Does it mean, that you can bring in a rigid system of communism or fascism ideology under that framework of “Life, liberty and the pursuit of happiness”? Obviously not, since those political ideologies would violate the basic framework of liberty in the political context. However, you can still have socialism as normative values within the frame work of “Life, liberty and the pursuit of happiness”.
Now apply the same concept to Hindu religion vs a vis other religions. There is no set ideology that Hindus should adhere to, to be a Hindu.. Hinduism is freedom of spiritual quest for an individual as long as the framework is not violated. if you insist that your belief or ideology is the only true one and the rest are false or that every other faith except yours is in violation, then you are violating the basic freedom of spiritual quest and most Hindus would not accept that as being Hindu.
Another illustration is how western liberal ideology is pilloried by some conservative societies of the world by pointing out to the worst in western civilization as an excuse for they not adopting a free society. e.g. They often point to pornography in the west as failure of a free society. They conveniently do not realize that westerners do not necessarily celebrate pornography instead consider that a price they have to pay for living in a free society.
Let me apply that to Hinduism. Because there are no rigid rules nor any Institution to enforce any in a “libertarian” faith called Hinduism, naturally you would find some odd and strange practices within Hinduism including some bizarre Tantric rituals and agories. Missionaries and religious supremacists and leftists often highlight these outlier sects/practices to point to the failure of Hinduism just like countries that have a tyrannical political system who point to pornography as the central tenet of free society to rationalize the supremacy of their tyrannical ideology/belief system. Most Hindus would tolerate these bizarre tantric practices (within the context of a law and order) but not necessarily celebrate them as Hindu rituals/customs. When there is no institutional organization or founder or a book then anyone can try to box it according to their own whims and fancy. This also provides ammunition to the anti Hindu leftists like Wendy Doniger (the alleged Hindu expert of the western academia) to “define/box” Hinduism by way of cherry picking stuff to her own perversion.
Process of scientific quest: Scientists and the process of scientific quest is about the pursuit of that never reaching wall of absolute knowledge. Its the pursuit and not necessarily about finding all the answers there is to know. They constantly keep pushing that wall of ignorance a little further and the constant debate to fine tune. Yet, you would find some individuals (Creationists) who would use this as a weakness to deride scientists and what they do for they claim their Green Goblin up in the heavens has created it all.
In Hinduism, its not about a set of revealed set of truth given to 1 or 2 individual that has adjudicated all questions and that subsequent generation would just have to accept this “adjudicated revealed truth” into perpetuity and that they would be punished if they challenge these “truths” (“Revelations” are really hearsay packaged as Truths). Instead, Hindu beliefs are really musings of individuals over 4000 years. Its intuitive perceptions of seers while introspecting and meditating deeply without guarantees to what they say is the absolute truth (They are opinions). Its devoid of compulsion by way of intrinsic threats for one to follow and believe what they say. These musings still continue and will never end just like scientific musings are a never ending pursuit.
Remember this axiom. “A person has a right to be wrong in their opinions but no one has a right to be wrong in their facts”.
Rig Veda. Genesis
HYMN CXXIX. Creation.
THEN was not non-existent nor existent: there was no realm of air, no sky beyond it. What covered in, and where? and what gave shelter? Was water there, unfathomed depth of water?
2 Death was not then, nor was there aught immortal: no sign was there, the day’s and night’s divider. That One Thing, breathless, breathed by its own nature: apart from it was nothing whatsoever.
3 Darkness there was: at first concealed in darkness this All was indiscriminated chaos. All that existed then was void and form less: by the great power of Warmth was born that Unit.
4 Thereafter rose Desire in the beginning, Desire, the primal seed and germ of Spirit. Sages who searched with their heart’s thought discovered the existent’s kinship in the non-existent.
5 Transversely was their severing line extended: what was above it then, and what below it? There were begetters, there were mighty forces, free action here and energy up yonder
6 Who verily knows and who can here declare it, whence it was born and whence comes this creation? The Gods are later than this world’s production. Who knows then whence it first came into being?
7 He, the first origin of this creation, whether he formed it all or did not form it, Whose eye controls this world in highest heaven, he verily knows it, or perhaps he knows not.
“The Hindu religion is the only one of the world’s great faiths dedicated to the idea that the Cosmos itself undergoes an immense, indeed an infinite, number of deaths and rebirths. It is the only religion in which the time scales correspond to those of modern scientific cosmology. Its cycles run from our ordinary day and night to a day and night of Brahma, 8.64 billion years long. Longer than the age of the Earth or the Sun and about half the time since the Big Bang.”
― Carl Sagan,
The above is true of Hinduism (Sanatna Dharma) in a philosophical sense. However many practice the religion with some specific belief set. Though they are not compelled in anyway to such specific beliefs.