Overall the sound quality, reliability and asthetics of amplifiers at any given price point is far better than it was even 10 years ago.
Obviously some older, more costly amps and the odd "classic" design give excellent results and offer S/H value for money way in excess of a more modern but modestly priced design.
One only has to look at the internal build quality of many modern amps to see that improved QC, leaner production costs and increased competition in a shrinking 2 channel market, allied to better quality modern parts has improved the lot of music lovers greatly from a value for money perspective.
Far more endemic is the belief that bright and detailed is how hifi should be and that means, to my mind, many older amps sound far more acceptable in the long term, perhaps this is one of the reasons for the resurgence of valves?