It’s true. Siri has some serious downfalls compared to where Alexa and Google voice has increasingly improved in areas where Siri lags. Where Siri does really well is in house commands with controlling iOS functionality for the HomePod, AirPods, Apple Watch, etc. But where Siri struggles is providing relevant search information, misunderstanding various types of words, where Google has no issue in most cases. Siri needs the improvement with dictation and deciphering words. If they can improve in those two areas, Siri will be at the top. I think Apple knows Siri is behind, which is one of the reasons they hired Googles Chief of artificial intelligence to bring the necessary changes to better the Siri experience in iOS.
https://www.macrumors.com/2018/04/03/apple-hires-google-ai-chief/amp/