The events in this movie were sequel material
Disclaimer: I have only played the Ezio triology after giving ACII a go and becoming completely hooked. I loved everything about it: the historical setting, Ezio's epic journey, the cutscenes and amazing cinematic quality... I hated Desmond and having to go back to him, but I could recognise the great depth the present day context added to the overall story.
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Judging from the games, AND even the short films like AC Lineage, I had every reason to believe a real Hollywood production controlled by Ubisoft would be nothing short of amazing.
So when I went to see this, even without super-high expectations after the trailers, I was deceived. The parts I thought would be difficult to capture faithfully like the stabbings and the leap of faith were actually not bad at all, and nothing I saw was actually disappointing - the problem is that even after months and months anticipating this movie, I must have forgotten everything about the characters less than 20 mins after leaving the room.
The main problems I found with this are that
a) we never get to care about any character, present or past.
b) they should have used the first film to properly set up the story and universe, and left the revolt at Abstergo for later. We didn't know or care enough about the characters to be excited about what was happening. It is natural sequel material - think Hunger Games. As it is, it just looks ridiculous that they wasted a film building up for this since now we're never getting a sequel.
This might have been saved if Cal Lynch's character had been truly memorable, but he wasn't and his back story was so unoriginal that what we got was a 2h-film with the worst of the games. I can't even say there are 2 parallel stories because we never get to know anything about Aguilar to care about him, same with Maria and her death.
AC isn't AC without the past, so the present-day plot must develop at a much, much slower pace than the past otherwise there's too much going on for a (2h!) film and both will lose out.
I think it was great they decided to have a proper present day story, but in the games we know the present day is just a pretext to plunge into a new story every game while providing a common thread to the whole franchise, with an additional, very useful purpose: since we don't expect much from the present-day in each instalment, they can continue the franchise indefinitely with new stories and decide to wrap it up by concluding the present-day whenever they want. By completely rejecting the present as a framing device, the past scenes in the film just look superfluous to those who don't know the games and an immensely wasted opportunity for those who do.