Some choices mattered, others made absolutely no difference... it just depended on who was writing the particular scenario. The stuff with the quarians and geth? That mattered... the stuff involving the rachni? None of that mattered.
I enjoyed playing Mass Effect 3 as well despite whatever story asshattery there is and design it having janky gameplay that was stripped back far too much and oversimplified to the point where you only have to spam one attack to clear an entire room in seconds. The Quarian-Get war and the Citadel DLC are my two favourite parts of the entire game despite it having the worst ending possible for a game where your choices are meant to matter, as told to you by the developers countless times.