I've been told that Mahayana was a schism and those responsible are burning in the worst of hells. I've been told that Mahayana is invented by renegade monks drunk on samadhi or worse. That it is a forgery, a heresy and a perversion of the Buddha's teachings (the last instance of this sort of thing was not too long ago on this forum). And of course I've been told that Mahayana is arrogant, supremacist and supercessionist. All of these I have heard from multiple sources both in fora and "meatspace".
It probably doesn't need saying that when one's faith in Dharma is not yet firmly established, such sentiments hurt and undermine everything one has managed to achieve in practice.
What I see as a practitioner are a collection of wisdom teachings that in practice have helped open my eyes a little, develop more clarity, patience and compassion in dealing with myself and others. In practical terms I haven't found anything that contradicts what I have learned in the Suttas although there are scholarly differences that may be relevant to other people or at other stages. The Bodhisattva orientation is perhaps one exception.
I should perhaps add that the later genesis of all Mahayana Sutras is not commonly accepted in Mahayana. I don't think my teacher who is a monastic of many years particularly minds one way or another, but Red Pine, who is perhaps the greatest of the translators of Chinese Mahayana literature (though I will defer to Ven Huifeng on that judgment) does not hold much stock by the current academic consensus on this matter. I am no expert and so I don't hold to a view here.
But to me if the Buddha's teachings are worthwhile then people have become liberated in the last 2500 years and these people could have elaborated on his teachings and adapted them to their culture and times. Modern Theravada teachers do that too and to me it is nothing but our Judeo-Christian bias that is responsible for the distaste many feel for such "innovations." Ajahn Sumedho's Sound of Silence meditation springs to mind and of course the never-ending debate about the Burmese vipassana. Whatever helps you get to the other shore, I say, and we are all different. Some may need only the Pali Suttas but for others different methods work best. In any case if you have not yet crossed to the other shore, what makes you qualified to say it must be "nothing but this"?
Sorry for the long-winded post...