My expectations were not particularly high beforehand, but some moments made me shake my head. I will also spoil some things.

At first, the first 8-10 episodes were not a problem. While some things (cough CGI dragon cough) looked awful, overall the visuals were extremely satisfying and the music was fine too.
I also liked the premise, though overall the anime doesn't really have much to do with MMORPGs. There are things like "death animations" and every now and then defeated enemies drop items, as is common in RPGs, but there wasn't much else.
There were a few times when interesting topics were addressed, such as some SAO players not being able to withstand the pressure and thus killing themselves, which I quite liked.
To be honest, I can't think of anything more positive to say about the anime.

It starts with the overdramatic portrayal when unimportant characters die.
In one of the very first episodes, as far as I can remember, a commander (name forgotten) died, and there was great mourning for him. But there's the problem that the viewer was never given a chance to get to know this character beforehand.
It's so ... What now? Was that where the producer of the show now imagined the audience empathising, or how was that meant to be?
Well, it continues with the fact that the main character Kirito turns out to be an extremely experienced player during a fight, although he was portrayed as very inexperienced a few minutes before. How can that be?
I think you can see what I'm getting at: logic flaws.
The example I just gave (which happened very early on) is forgivable, but when the entire arc of tension is built on the characters being tied to their real lives through SAO and thus dying if they lose, but that arc of tension is simply removed during the final battle to let Kirito and Asuna win, it really hurts.
Add to that things like the antagonist's non-existent motivation (he thinks he forgot about her → remains unrevealed for the whole time) or annoying harem elements.
Another big problem would be that the protagonist has practically no real character.
Due to the many timeskips, he is constantly rewritten from episode to episode, so in one episode he is the "nerd" who hardly has any social contacts and seems to hardly ever go out or do anything else, while in the next episodes he is the man par excellence that all the women go for.
Apart from that, the romance that builds up between him and Asuna is not exactly successful.
It practically comes out of nowhere (Kirito = Mary Sue and everyone just thinks he's cool) and is extremely predictable and overplayed.

Probably the biggest problem of the anime, however, is the Alfheim arc, which takes up the last 10 episodes of the anime.
Not that Asuna presented herself great in the first arc, but after that it is quite a bit worse: she is practically degraded to a sex object, hotly desired by the antagonist. It is incomprehensible to me how a protagonist can be so violated.
Apart from how much fanservice has increased in general, especially compared to SAO, the antagonist is basically just out to rape Asuna, and there are even two scenes where she is (almost) raped.
Other than that, there's nothing much worth mentioning. The plot of the arc is to free Asuna from her prison and defeat the villain.
Then we have "incest interludes", in that there is something going on between Kirito and his sister. What was that in it for? I don't get it.
The sexual interludes didn't mesh at all with the otherwise adventurous idea of the series, which sort of destroys its mood building.

Conclusion:
With this low rating I'm giving a very harsh verdict, but it's not even close to a better one, on the contrary:
You can be glad that I don't give the series a catastrophic rating because of its few good aspects, because there wasn't much missing and it would have deserved one.