Genetically, culturally and mentally Czechs are definitely closer to Celts, Germans and Austrians than to Serbs, Poles or Russians. They also have the highest concentration of R1b (Celto-Germanic haplogroup) compared to other Slavs.
Even their language is very different from other Slavic languages. Slavs can't understand what Czechs say, even though they understand separate words. When I first heard Czech, I thought it was Dutch, Finnish or even French lol.

Why shouldn't scientists exclude Czechs from the list of Slavic peoples?