Be honest please

"I can't stand when those vintage guys boast how great the receivers were from the 70's. I owned some of those receivers as a kid and I can tell you they don't hold a candle to what they are making nowadays."

Maybe they buy vintage gear because they prefer it. Also, I don't think you would take issue with someone for "boasting" about equipment you like. After all, your opinion is fact.

I don't look down on people finding gear at low or no price.
In general, however, bragging is not a pleasant behavior to endure.

Should that bother me?

Like the old saying goes," ONE MAN'S TRASH IS ANOTHER MAN'S TREASURE."

The operative word is "bragging" that triggers a certain response.
Bragging high or low is rarely an admired trait by third party witnesses to the said bragging.

Why?

(1) Taters nailed it. As in life in general, you invariably only get what you pay for.... Full stop.

(2) Then those certain types publicly "bragging" in open forum about throwing around nickels like they are manhole covers, and extending the bragging further with their solely anecdotal heavily biased personal value judgements about how great the gear performs vis-a-vis today's equipment; won't garner much support IMO. Would they repeat their dumpster diving bragging using their real names and direct contact information instead of hiding behind that central plank of anonymity provided by the forum pseudonyms..... Hmmm.... Dunno..... but I doubt it.