The term "innovative" may be perhaps a bit extreme here. Siege represents a refinement of specific ideas that we have seen before and if you are looking for a 5v5 competitive focused shooter, there is probably not much better than Siege but I don't think it really counts as "most innovative".

Here is the thing. If we were to turn back the clock to the late 90's and call the original Rainbow six title "the most innovative FPS in the last 10 years", you would be absolutely correct. No other shooter (at the time) had even attempted to do what it had done. While other shooters were still slowly making the shift from Doom/Quake style to a more narratively focused one. Red Storm came in with a shooter that put realism at the forefront and added so many previously unseen mechanics in the process. It could truly be called a innovative, not iterative, innovative.

If I were to compare Siege to a game that came out around the original R6's time frame, I would say it shares some similarities with SWAT 3. That title borrowed heavily from a variety of other games but added its own spin on them. It was not a incredibly innovative title but it was masterful in its iteration.

Coming from the perspective of a long-time fan of the older R6 titles, I gave Siege a try and found that at its core, it is designed to pull from the Counter-strike playerbase. It is built firmly on that foundation and while it does indeed have some gameplay mechanics that are iterations and refinements on other games (destructable environments pulled from Battlefield and Red Faction but more refined. Class system from a variety of titles, recon elements with mechanical similarities to Call of Duty's drones and even titles like Splinter cell, etc, etc).

In the end, Siege is a 5v5 competitive shooter with short round times and fairly small maps designed for fast paced action. It has some additional elements placed on top of that but those elements don't change that Siege is not exactly "the most innovative FPS of the last 10 years" but instead a excellent refinement of mechanics that we have seen in a variety of titles placed atop a worthy CS competitor.

Sad enough, if Ubisoft were to make a Rainbow Six title that is simply a more modern version of the original three titles, it would probably get a reaction that is not too dissimilar to the reaction the original got since no other shooter franchise has done something similar in _years.

Please keep in mind before you hit that downvote button. I am not saying that Siege is a bad game or that Siege is "just like" Counter-strike. I am simply stating that calling a game like Siege the "most innovative FPS of the last 10 years" may be a stretch. I can appreciate that the writer and some posters here are big fans of the game and want to sing it praises (we all do it) but when you step back and really look at it, I don't think it actually works out as "most innovative" and that is not a bad thing.