After reading some of the top-rated reviews online I find myself disagreeing a lot with them.
To me, Yesterday was never about the Beatles — The Beatles served as transport for the theme of "the meaning of life." It's a film about fullfillment and finding joy in existing. Of course, the Beatles are honored as one prime example of what brings joy and fullfillment to people but neither the plot nor the story revolves around them — in this movie's universe they do not even exist.
In the first two (major) parts of the movie I found myself entertained — I laughed and felt shame and excitement. At the very end of the second act and the beginning of the movie's end, Jack, the main character, drives to a house by the beach. I felt the movie, in that moment, had elegantly led me to the thought of contemplating the meaning of life, what it is to feel joy and why it matters. Sadly, hollywood (as is often the case), underestimated its audience. What could have been a, mainly, tender and comforting moment for us through the characters' dialogue ultimately turned into a banal and bold neon sign advertising what the audience "impossibly" could have contemplated on their own — embarrassing. To be honest, if the movie ended just as the door opened, or even after a simple shared greeting of the characters, that would have been better than this scene that reminds me of a novel's author writing a foreword on how to read the book. Sadly, this is not where the disappointment ends for me. For some reason, the main character decides on performing one of the most self-aggrandizing and unempathetic acts of "love" I have ever experienced — and even worse: It works. The climax is followed by unnecessary clarification and what seems like a kindergartener's idea of romance — and not in sweet way.
All-in-all, the movie was enjoyable and I even found it very well-crafted until its ending moments. The final chord struck will always leave a strong impression.
TL;DR:
The movie could have ended while it was grand, before it got bad.