Let me answer those points one by one :
There is no Messages option available in this site, as is available in
Quora and Facebook, through which we can send our message direct to
the person concerned
Seems the short answer is No and Never, and has been explained in great detail here :
Any way to send a personal message to another user?
This site is dominated by Vaishnavites, a sect in the Hinduism and who
are not tolerate towards others opinion. Many a time my answers are
downvoted just because they are against the principles of VAISHNAVISM.
I am a relatively new user at hinduism.stackexchange, and have been a while at other stack exchange websites. I see that this observation of yours, may be truly felt by you, but unfortunately, it's a subjective one and cannot be established by data.
There are only two sources where one can look for substantiation, profile description and answers-comments.
The profile description at any of the stack exchange websites do not require the declaration of certain faith or sect or programming language, or adherence to it. One can pretty much write anything in the profile descriptions and still not adhere to it. Yet others may write nothing and but still adhere to it. For this reason, I twinge when I see references in the comments that say, aren't you a Saivite, aren't you a Advaitin and so on. How does it matter what I profess or practise, the answer or the comment should be judged by its own merit and relevance to the question.
Similar is the inference drawn from answers. For instance, Joe may believe in all kinds of things at the same time, some Vaishnavism, some Saivism, some Vedanta, and some modern masters such as Ramana, Ramakrishna or Sivananda. Even if in your specific context, you are able to establish that all your downvoters have an X inclination, that is not enough.
I think the problem cited at Sl.No.2 may be major impediment for
hampering the growth of the site
The key issue is : how can a website like Stack Exchange, which is totally community-driven and community-moderated, determine algorithmically or by a set of volunteer processes, that such-and-such sect is dominating such-and-such forum ? The problem is all the more complex in the case of Hinduism. It's not like the Python language, where the Python language manual is the final reference for all things under the Python sky. Masters, doctrines, scriptures and texts have come and stayed and gone, some of them, historic and some of them not, so how do you establish that a certain viewpoint is Saivism or Vaishnavism or not ? The only source, in addition to the assertion of the post-writer, is the scriptures and they can vary hugely into lanes and bylanes of text that were specific to geographies, times, and languages and contexts in which they were composed. For instance, the Ramcharita Manas, the Kamba Ramayana or the Adhyatma Ramayana narrated by Shiva to Parvati, is as much Hinduism as the Valmiki Ramayana, so which of these is considered a final version of the events ?
In comparison, consider Stack Overflow, the programming forum. It's known that some programming languages are widely present, widely asked and widely answered. But that's all driven by the people who sign up, the ones who post and the ones who moderate, which is again driven by their activity and their editorial volunteering.
The subjectivity of determining this is hampered by the fact, on the Internet, people can present themselves to be what they want. For instance, see the discussion on male domination here:
Stackoverflow is male dominated
How does one know who is male or female or Saivite or Vaishnavite or fake theist and more importantly, how to determine it programmatically ?
So there would be no point blaming that your downvoters belong to a certain species. The forest is such. Let's all enrich the forest by making a more diverse ecosystem.
These 2 problems that I have identified are brought to your notice. It
is upto you, to decide as to what action to be initiated for the
improvement of this site
Whether it is fortunate or unfortunate, many of these are standard constructs of Stack Exchange fora. It's well-known outside Stack Exchange that SE does provide X,Y and Z elements of a Q & A environment and does not provide A,B,C features by Quora or P,Q,R features of Facebook, and there is resentment about it. The oft-heard response within SE, tends to sound like, 'we are what we are, this is what we offer, if this is what you are looking for, this is the place for you, otherwise, there are a lot of other places'.
This can sound a tad harsh, it sounded like that to me in the early days of SE. But then, the overall goals of SE, seems to be to keep:
(a) the quality of questions high
(b) the quality of answers high (both of these require downvoting and flagging)
(c) what is high and low be determined by the user community and
(d) may the best users in the community, as seen by their acts of contribution and by other users, rise up to be the moderators.
Once we understand this model, and it is we who build the model, we can hopefully try to work within those borders to build a great one-stop shop for all Hinduism-related answers. Like others have said in the comment, stay with the site, because, if your complaint is that the site is not diverse enough, the best way to address that is to add to it by one's own presence and consistent contribution.