Way to go! Yes, you can get faster because you started late. You've probably got another 2 years of that. Keep at it. OTOH, at our age keeping our speed the same year-to-year actually means we're getting faster. My wife and I did a 24 mile loop on our tandem yesterday that we've done many, many times. Out of 13 Strava segments, we PRed 7. We only tried for it on one, missing a cup by one second. We're 136 y.o.

We can't train harder, so we have to train smarter, which is what you did.