It's not utterly awful, it just lacks of many elements that could've made the saga much more valuable.
For example, starting with the friend group, it isn't a secret to no one that the chemistry between the girls was very poor. They started with an uncomfortable aura surrounding them, backed up by their arrogance and rudeness within each other from the very beginning. Which is not the problem at all, what bothers me is that they ended being very close to each other, completely missing the bonding that lead to their relationship to change. They just expected the audience to believe they were now friends without showing the process.
As fot each character, they were very bland. Not one to be completely relatable or likable for the audience.
Stella had an incredible background, which could have been used as the reason of her actions, however she was just displayed as the mean girl that everyone hates and suddenly acting as a good friend in the last episodes.
Terra was the character that infuriated me the most. First, they white washed the image of flora (as they reffer to her as terra's cousin, which implies that flora may be white as well). In Terra we could have seen a strong, intelligent woman that goes against the patriarchy. Instead they showed us the comedic relief (as in every other show that wants to include plus size women) that just talks too much and is annoying to her friends.
Aisha was so dissapointing. She was one of the best characters from the start, but missed completely the opportunity to develop her, which ends on her being just the token black character that always works in favor of the main white character.
Musa was left with an almost useless power, and also lets not talk about the whitewashing as well.
And Bloom, the main character, is probably the most boring of them all. Dislpayed as the stereotypical "i'm not like other girls" type, and even though she is the character with most time on the screen, we still are left with a bland character.
Not to mention, the romance on Fate is almost dead, with Sky's and Bloom's relationship being completely bland and lacking on chemistry. They could even have inserted some drama between Sam and Musa, using Terra as the wall between them, but that clearly didn't happened.
As for the the kingdoms, realms, and the boarding school (Alfea) they left so much holes to be explained. It was an incredible opportunity to expand the Magical World and explain it so much more.
However not everything is bad. The saga used very advanced special effects and CGI. The school was a very adequate scenario for the saga, and every little scenario they showed was very well decorated and adapted. The outfits though, could have been so much better than they were.
In conclusion, i think that if Fate was given more than 6 episodes for the first season, they could have explained and develop many elements that were untouched, which is the exact reason that I will be waiting patiently for another season.