If your bike has 130mm spacing and you don't feel the need to get disc brakes, you're probably fine just upgrading components.
I ride 2 steel bikes, both "modern" but also 20ish years old.
The road bike is set up with 10speed Campy Chorus that I upgraded cranks to a carbon compact UT. I switched to a carbon fork for fit issues too. On the nice wheels, I'm just at 17.5 lbs. Add a pound for my Open Pro workhorses. I am an ok climber, I drop more people than I get dropped by. This early aught bike rides modern and fast and certainly doesn't slow me down. It has never been the reason I've crushed souls or been crushed.
The gravel bike is a different story. It's a cross bike that takes wider tires. It's a bit of a Frankenstein build. It works super well but it has toe rub. For gravel, I'd prefer disc brakes. If I damage my tank of a fork, there isn't anything with a 1" steerer tube to replace it with. If I were to do that build again, I'd probably go a lot more modern.