Fashionable concepts or an established traditional system in QA?

What to choose in QA: fashionable concepts or an established traditional system? 

I am a QA Lead at Kupibilet and I will tell you how we tried to invent a bicycle, it didn't ride and we were left with the current process. 

 I will share my personal experience of simultaneous implementation of two different approaches in testing within the same company. I will tell you why the established system turned out to be more efficient and more viable than fashionable concepts, and what new approaches and techniques have taken root in the company after all.