If you want the truth, watch a documentary. Fiction has ends in mind other than transmitting facts.
Turing wasn’t even depicted as gay in the movie (apart from a couple of random comments).
And incredibly, they didn’t cover any of the details of his death. Apparently he was obsessed with Snow White, hence the apparent suicide (or experimental mix-up) with a poisoned apple. How could you make a Hollywood movie about his life and not even touch on his connection with one of the key Hollywood milestones? It’s very strange.
Apart from that, it persistently gave the impression that Turing was a lone genius and minimized the contributions of everybody else. That’s a mis-service to everyone, including Turing, who comes across as a very poor team player.
And apart from all that, I simply didn’t think it was a very good movie, taken as pure entertainment. I know people who loved it, though, so I realize opinions vary. It’s hard to separate my opinion from my biases around the treatment of the subject matter.
The movie dances gingerly around the subject in a manner that’s the exact opposite of Turing himself, who seems to have been “out” to a dangerous degree (for the 40s and 50s). His friends warned him to be careful. None of that is in the movie.
Honestly though I see your point, because they did show the flashbacks to his childhood as some sort of vague attempt at character development. Might it have been best to just not discuss it altogether? You could argue the story is "dramatic" enough without it (winning a war!). To try to do both in 1.5 hours or whatever is asking a lot.
There is precedent for all of this...it can be done and done well. The obvious comparison is "A Beautiful Mind" which takes a similar sort of framing story (brilliant academic's personal and professional life). They pulled it off there IMO and just weren't able to balance both here.