I've been roleplaying for over 20 years and have played and run over 30 different roleplaying systems and no game has ever bugged me like the Infinity RPG.
I am directly bothered by the whole concept of the 2D20 system. The Momentum and Heat system limits the ability of the game master to tell an exciting story adapted to the players. Unless he completely abandons this game mechanic. Momentum points are a chore.
Worst of all, however, is the poor quality of the rules system. There are very many game mechanics and they are poorly explained. There are hardly any examples and they hardly explain anything. Each piece of equipment and each talent has its own rules, and of course you are supposed to keep all of them in mind. The rulebook then cheekily gives the tip that you as a game master should know the rules especially well. Great! Write simpler rules and explain them better!
Another point are the drawings. They are nice, but totally random. They rarely have anything to do with the text section. Alien races and special human units are not shown graphically, so you have to bring your own background knowledge to know what they even look like.
And this lack of a concept carries on through to the adventures. Again, appropriate graphic representations are missing and there are even two maps where the same building looks completely different (Acheron Cascade). And the adventures can really only be described as story hooks. Since scenes are not always logically connected and there is just so much information missing that the game master would have to write almost everything himself.
The only positive thing about the Infinity game (and all other 2D20 products from Modiphius) is the fluff. We will continue to play and use the fluff, but use a new, a good system for our adventures.