I've got a 20-year old custom steel racing bike. It's a beaut, but there's no denying that there's been a lot of innovation in cycling in the meantime.
I also just got a year-old NOS bike to use as my commuter. It's got all the modern bells and whistles. I was interested in seeing how it rode on a 20-mile route I ride a lot, and took it out this weekend. Result: 41 seconds ahead of my average, but at an average speed 0.8 mph slower than my fastest on that route. So, you know, nice, but hardly world-changing. If I were worried about getting dropped on a group ride…I'd still get dropped.
The new bike is nice in ways that don't really make you go faster. The hydraulic discs are great. The fatter tires smooth out the ride (my old racer has brutally short chainstays and probably couldn't accommodate 25-mm tires). I haven't made full use of the 2x11 drivetrain because with the wider cassette, I haven't had to put it on the little ring. The bike is startlingly light. I've been impressed at the advanced specs that are available in a nice but not elite bike.
Putting more gear on your old bike might benefit you in some ways, but they won't make you faster apart from some edge cases. Most of the additional gears you get with an 11-speed drivetrain are at the low end.