I need to preface this by saying 2 things.

First, I used to be a MASSIVE sao fan. So much so, that I had it as my wallpaper for everything, I had it rated as a 10/10 and I even did my 3D animation project in high school based off of the swords from the anime. It's no understatement that I absolutely LOVED this show. But when you grow older, you can begin to see the past without rose-tinted glasses. And with that unclouded judgement, I'll go over what went wrong in the anime.

Secondly, the argument that the ALO arc shouldn't be judged alongside the Aincrad arc is complete bullshit. They are BOTH part of sao and thus share the blame for sao's faults.

Now, let's get to cracking. I'll start off with what very little pros we have and follow it up with the plentiful amount of cons.

Sao has a really, really strong start. It's first few episodes are really great, and set the atmosphere really well. It does a great job at introducing Kirito and Klein too.

Sao also recreates a very realistic portrayal of MMOs. The world building is one of the only things that keep this anime afloat.

Sadly, that's about it for the pros. Moving on to cons, first we have:

-Rushed pacing. You really feel the skipped content like Asuna's backstory of joining the blood oath, Kirito's backstory of being a "beater" and most importantly, the dozens of floors skipped throughout the story. 

-Dogshit villains. Each of the 3 villains are "bad just to be bad" and it's really disappointing. Kayaba just wanted to make a killing game for no reason. Laughing Coffin just wants to kill people for fun. And Kuradeel just wants to rape Asuna. Can we get a round of applause for such understandable and sympathetic villains? /s

-Plot holes that make this shit look like swiss cheese. How does Asuna magically break out of paralysis to save Kirito? Why does Kirito spawn into ALO right next to his sister (which is bullshit for it's own reason) instead of in Spriggin territory? Why does Kirito keep his stats and abilities from Aincrad instead of starting fresh like everyone else? Why does nobody in Asuna's family/hospital staff realize a man is sexually assaulting her while in a coma? Bringing back Yui from the dead was also a bullshit deus ex machina move. There's so much that breaks the great setup they had in the first few episodes.

-ALO. I don't think I need to elaborate too much on this. ALO was just the Aincrad arc but with more tentacle rape, incest, deus ex machina, and regular rape. Most people already know ALO sucked ass so I won't waste my breath on that.

All of these cons are huge blows to the anime overall, and the few pros that do exist get overshadowed by a very large margin. 4.1/10.