I… don't even know where to begin. You seem to put yourself in the role of a messenger for "regular people" as opposed to the "critics". You also seem to have a recipe for making a classic film. Well, let's go over that assessment.
Let's just say first that the film is already a huge classic. It's being lauded often for one of the best war films ever made and in general. It was a box-office hit in the Soviet Union, so it worked for a lot of "regular people" (almost 30 million admissions in that country alone). So it's hardly some kind of a critic ghetto film that you're trying to corner it in. There are places other than the US where movies can be hits, you know. It also wasn't a low-budget movie, which you seem to imply. The surreal feel of the film, enhanced by what you call "unrealistic dialogue", is intentional due to the disorientation and utter horror surviving children had experienced in the midst of a genocide - and bore testimonies after the fact, which was used as research basis for the film.
Which leads me to my next point. You seem to presume that no "actual research" was made for the film. The screenplay was written by somebody who was with partisans in Belarus during those events. Interviews were made with witnesses of the massacres. Research began 8 years before the movie was finally released. It was made in the country where the massacres occurred, in the language of the people. Something that many American movies, such as Schindler's List, do not necessarily do.
I don't mean to discredit Spielberg and Saving Private Ryan too much, since I do like the film, but its sentimentality and on-the-nose ending is one of the reasons why Western audiences find it easier to swallow. Schindler's List suffers from a similar syndrome (for a more honest and slightly less condescending depiction of the Holocaust - I find Claude Lanzmann's Shoah and Alain Resnais' Night and Fog to be far more powerful experiences). As Terry Gilliam had said, Spielberg offers nicely wrapped answers in his movies. Klimov refuses to offer such privileges to the viewer.
Realistic battle scenes? First of all, the plot of the movie doesn't necessitate big battle scenes. Secondly, there is one riveting scene of an organised massacre that I find to be gruesomely authentic.
Characters were based on real people. But I fail to see how would that make the film necessarily more realistic. It could precisely have the opposite effect. One of the main criticisms that Schindler's List frequently gets is that it greatly exaggerated the Oskar Schindler character, particularly in that weepy "I could have done more!" ending.
Seriously, not liking the film is perfectly fine. Making stuff up about how it was poorly researched is really stretching it.
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