Over the last 10 years, I have bought and sold quite a few pieces of gear ranging in age from 75 years old, to less than 10 years old. I've reduced this collection down to what I consider to be the best pieces. These are my opinions, far from gospel.
My tube separates, integrated amps, and receivers from companies like Scott, Fisher, Acrosound, Pilot, and Grundig, when paired with the correct speakers, can rival even the most expensive gear for sound quality. For the most part, these devices can last forever with a small mount of maintenance and care.
My solid state integrated amps and receivers also gold their own against newer gear I've demo'd. These pieces range in watt output from 30-100, and again, paired with the right speakers can rival some quite expensive gear. These pieces from Luxman, Marantz, Sansui, and Harman Kardon offer excellent value and sound quality.
For more established folks that have high levels of disposable income, there are wonderful newer products available that can offer pride in ownership as well as fantastic sound quality. For those of us that have less disposable income, but still desire excellent sound quality and pride in ownership, there are quite a few vintage pieces that can fill that need.
It boils down to personal preference, and there is no one size fits all solution. The only way to prove or disprove your theory of old vs. new, is to start setting up systems, listening, buying, selling, and swapping components to see for yourself. I'm a strong believer in the fact you can't buy you way to the top. It doesn't matter what your hobby is, the most expensive item will not make you proficient in that hobby. You can buy the most expensive sports car, but if you can't drive it, it's only a showpiece. You can buy the most expensive fire arm or compound bow, but without practice, these won't perform any differently in the hands of a novice. You can spend piles of money on expensive audio gear, and without proper set up, and room conditioning, they become show pieces easily bested by much less expensive gear.
Only you can decide what you value most in your system. There are quite a few pieces of gear I would love to own and live with. Most of these pieces I can buy any given day new or used. I place a very high value on my vintage tube gear. Some of these pieces would take years of searching to replace. I'm not willing to make the trade from something rare, to something common, only to find its a lateral move in sound quality, or only slightly better sounding. My end goal is always enjoying the music.