Ignoring both the EA - NFL exclusivity agreement (other people have already told that story) and the litany of football strategy features not present in NFL 2K5 relative to modern football games on account of its advanced age, I think people either forget or deliberately omit the glaring problems present in NFL 2K5 which dramatically hampered the experience both during its time of relevance and today, especially from the perspective of multiplayer and franchise.
For example, I gather you are a big fan of NFL Head Coach and similar single-player NFL team management games. In NFL 2K5 franchise mode, CPU-controlled teams
always and only select QBs, RBs, OTs, and DEs with their Round 1 draft picks. That bug was never corrected, and it is a crippling roster management issue for single player franchise gamers once you know it is there.
If I recall correctly, NFL 2K5 also had major issues with CPU trade logic, notably with CPU teams aggressively trading star players with one another. I recall the CPU Packers trading away Brett Favre quite often.
If you were a couch multiplayer gamer with friends, NFL 2K5 franchise mode was a logistical nightmare; you are only allowed to play the games in the exact order they appear on the schedule. In comparison, every Madden game of the era allowed for playing the games in a given week in any order. This shortcoming by itself stopped my high school friends from playing NFL 2K5 franchise with me, and as a result we played a ton of Madden 2005 Franchise instead with no regrets.
I'm not even going to touch the Weekly Prep feature, which was well-intentioned but so incredibly obtuse and opaque. I never figured it out. I don't know that anyone did. Player progression in NFL 2K5 was also chaotic and unpredictable. Maybe that's more realistic? But it certainly wasn't fun winning MVP with a young quarterback only to see his OVR rating
decrease the following season.
On the field, there were also significant issues. The most prominent one I remember is that offensive clipping penalties subtracted from a ballcarrier's rushing yardage. I believe this bug was corrected on XBOX with a patch, admittedly, but as far as I know it is still present on the PS2 version, which I think is the more popular version for emulation.
Further, safeties playing deep half zones in Cover 2 or Cover 3 middle third zones were also routinely seen running in tight semi-circles, which could get them out of position extremely quickly. I recall many many roster editors spending time "in the lab" so to speak trying to mess with all sorts of ratings to improve safety play; I have no idea how successful they were in doing so, but having watched videos of NFL 2K5 played on emulators as recent as this summer I know the problem is still in the game.
NFL 2K5 should be celebrated for its kitchen-sink design, its breadth of content and features, its fan service, its raising the bar for sports video game presentation and commentary, the VIP System (this in particular isn't talked about nearly enough), and its at the time good gameplay which on-balance at least held its own with Madden 2005 (it did some things better and some things worse). For franchise and multiplayer gamers, however, NFL 2K5 was surpassed a
long time ago.