Thingking that way even you dont know bitcoin that much is not really understandable well people talk about this way because they tend to criticize evrything even they dont realy know much about something. Nothing could replace bitcoin because it has a headstart of a years to grow than new cryptocurrencies.
It never be happen that other crypto currency replaced bitcoin because bitcoin have high Security system and high market value. Also bitcoin has high rising rate in the value. The popularity of bitcoin is also a factor that no other crypto currency can replace bitcoin. The trust of people everywhere in the world on bitcoin is very high is compare to another crypto currencies.