Sure, it might be AC1 in its "purest" form, but that is because it's just the first game, which sets the tone. I give it credit for doing that, but that's it. I do recall that at the time it was received relatively lackluster.
Exchange Odyssey with 1, correct for what the consoles and computers were capable for at the time, and you might say the same, that it would've been AC in its purest form, and nowadays it's all underbloated and too poor, not rich in detail.
Personally, I found the parkour in the first few games very boring. It certainly did have restrictions of movement. You could not climb outside city walls, or stones, or trees. May I remind you that games from III (when Desmond died) and on, actually started in that?
I fear your memory might be selective, but no one is holding you back from playing the older games. I personally prefer the newer ones as they actually do have deeper stories.
So, yes: I do give the first game crap, because it is not accessible for handicapped people (eg. a lack of good subtitles), and it was very glitchy (you could only attack the Lionheart when you pushed him through the corridor, when this was not intended gameplay). And all that, while it should have been accessible and less glitchy and repetitive, even compared to other games at the time.
You simply have a rosy coloured view of the past, I'm afraid; try looking more rosy towards the future, be thankful, and there may be less reason for chagrin. Have a good evening.