Between Play Now Live and Simple Season - functions both added into the game starting with Madden 18 - I think the people who just want to smash through a single season of NFL football without worrying about personnel, injury management, etc. are more than adequately covered. Adding a separate Season mode on top of that is a waste of time, IMO.
Tiburon is already addressing your concern. Per data mining of Madden 19 PC, the Simulation game style does not include the "perfect user execution" thresholds you're alluding to and fearful of. They are indeed present in Arcade and Competitive (the game style for ranked online head-to-head games outside of Franchise). For example, using Madden 19 for reference:
- Using the Simulation game style, there is a chance to throw an inaccurate short pass with no pressure and set feet even if your QB has Short Accuracy 99.
- Using the Competitive game style, there's a threshold rating which will guarantee perfect passes if met or exceeded (I believe it's 85 for Short Accuracy? Might be 90.).
- Using the Arcade game style, apparently all passes are perfectly accurate if there's no pressure and you're not moving, regardless of player ratings.
I assume that Madden 20 will behave similarly, with the additional logic of X-Factor and Zone abilities now also affecting the outcome. For example, Aaron Rodgers has the Roaming Deadeye ability, which grants him perfect accuracy on passes - ignoring his ratings entirely - if he throws a lob, touch, or bullet pass while standing outside the pocket and not under pressure.
Madden 20 also sets out to accomplish player differentiation further via spreading out player ratings.