[Selmo]

Yes, Tolkien was aware of modern political systems and of alternative class structures to his own romanticised view of the English class structure - and he disliked them all.

Tolkien was a "classist" in that he recognised that class structures of some sort exist in all human societies greater than a single family unit. To make his created world believable, he had to include this fact.
However, it's clear from his works that he did not hold the view that different classes should not mix (Merry and Pippin are close friends of the socially inferior Frodo) and Sam's rise shows that Tolkien approved of some level of class mobility.

Sam's rapid rise up the class ladder was not limited to becoming Mayor of The Shire, it went much further. His daughter and son-in-law led the expansion westwards, becoming Wardens of the Westmarch, equal in status to the Master of Buckland. His daughter became Lady-in-Waiting to the Queen, a position reserved for families of the highest rank. Sam himself was appointed a Councillor of the renewed Northern Kingdom, not just as an equal with the Thain and the Master but with Princes and Nobles of the Kingdom.
However, the thing that showes the attitude of hobbits to class movement most clearly occured when Sam was still a servant/gardener at Bag End. It was his relationship with Rosie Cotton. Rosie was the daughter of a prosperous and well-respected farmer, in status far above Sam who at that time had gained no reputation except as a gardener. That her family permited her to fall for, and later marry, Sam without, apparently, any comment, shows that class mobility among hobbits was normal.

Sam's rise isn't of the "poor widow's son makes good" sort. He genuinely grows during his year away from The Shire. When he returns, he is no longer Samwise (semi-wise, half-witted); he has grown in self-confidence, aware of his own worth and potential. Although he cannot throw off the habbit, or the desire, to call Frodo "Mr Frodo", he is no longer anyone's servant; he's his own man.

Tolkien himself experienced class mobility. His father was a bank clerk who rose to be posted to South Africa as a bank manager with a life of relative luxury (big house, servants, etc.). The family lived with poverty after the father's death but Tolkien won a scholarship to an elite school and then to Oxford University. He then became an Officer in the British Army and went on to become a respected academic as a philologist. His work was rewarded with a Professorship at Oxford, at that time perhaps the most socially prestigious University in the world. (Note for Americans: the role of "Professor" in a British University is a much more senior one than that of a Professor in USA).

Tolkien's rise up the class ladder was not as rapid as Sam's, nor did it reach as high but it ensured that his view of class was not as rigid as many of his contemporaries in the first half of the 20th Century.
.