A 2016 bike will only be marginally superior to the same spec level bike of 10 years ago. Even the high end stuff from the mid to late 90's is still plenty adequate for racing at an amateur to intermediate level.
All the things you listed as far as aero, comfort, weight, etc... is indeed a little better on the newer stuff.. But the difference is probably smaller than you think, and you can still spend your money more wisely. There are other things which matter alot more, such as a professional fitting, power meter, proper diet, coach, etc... If you haven't got those in check already, do that before you buy a new bike IMO.
Going fast on a bike is mostly about fitness. Anything under 20lbs with light weight stiff alloy frame, a wheelset under 1800g, good racing specific tires, and 105 level group is plenty to be competitive in local races and spirited club rides.
However, if you have a hole burning in your pocket or are really serious about going as fast as possible, a better newer bike will indeed make a small improvement in your times within single digit percentage level.
As far as comfort, I find even old alloy frames to be very comfy with the right wheelset, tires, tire pressure, and seatpost... And if you want aero, get yourself an aero helmet, have a tailor alter your clothing, and dial in a comfy yet aggressive fit. Those things matter alot more than an aero frame.
If your more of just a casual recreational rider, now is a great time to buy. You can certainly buy a newer bike and experience a more pleasurable ride. Ergonomics are better nowadays, you get a brand new crisp running drivetrain, lots more bike and component diversity and choices, etc.... It will certainly motivate you to get out the door and hammer it, which is a good thing for sure! Just dont expect to go much faster than your old bike...
Much of the modern features and innovations seem to be centered around comfort, and much more choices in things like geometry, tire widths, rim vs. disk brakes, aero vs. light frames, electronic shifting vs. mechanical, tubeless tires, wider gearing, etc... The choices are really endless nowadays and you can really get a purpose built bike made just for you vs. the 1990s when bikes were still lightning fast but with no choices. All horizontal top tube, straight block cassettes, standard chainrings, only 2 brands of power meters, traditional round tube frame shapes, no disk brakes, no tubeless, etc...
Sorry to bring up this old thread once again but i have a new situation to ask about. I tested some aero frames(Pina F8/Madone 9/Aeroad 2016) and found the bike to be slightly faster than the old look 595, maybe around 1-2km/hr at most with the same effort. sometimes it just make me wonder to think about let´s say i am riding with a fast group and i am just lacking slightly behind with them with my look 595, and getting the newer aero frame will increase the overall speed slightly as it is faster by a bit. in this case i will be able to catch up with the fast group. OR what else can i do if i were to stay with the look 595 to increase the speed and ride with along the fast group riders. My fitness/diet/bike fit and bike set-up is already at the optimized stage but not sure whether is it really the bike that is making the slight differences here between me getting slightly lacking behind or be able to ride along with the fast riders, the average speed we are going at for fast group is about 38-40km/hr