We weren't alone in that belief: With the enamored gullibility of the 1950s, (It was 1954 when, at the age of twelve, I first became a "HiFi Crazy") most people believed that electronics were "scientific", and therefore as near to perfect as anyone could ever want. The magazines of the time (Popular Electronics and High Fidelity) largely agreed, and most of the early "authorities", the most influential of whom was almost certainly Julian Hirsch, said that it was the electromechanical parts ― the cartridge and the speakers - that, because of their less-than-perfect mechanical limitations, were responsible for most of the sonic differences between one system and another.
Even though we all lusted after a "Mac 30" (or even, please God, a "Mac 60", please, please) it seemed perfectly reasonable that the electronics weren't going to make any difference to the sound: After all, all of the electronics of the time claimed THD and IM distortion figures of less than 1% (certainly, we thought, no one could possibly hear that little distortion) and all claimed frequency response of 20 to 20,000cps (We didn't use "Hertz" [Hz] yet), plus or minus no more than 3dB. That was far better than the response range of the available records at the time (the typical frequency response range of even the best tape recorders, microphones, and disc cutting heads of the day was only claimed to be 50 to 15,000cps +/- 3dB) so we were perfectly happy with our home-built Heathkit or EICO electronics, and gave no thought to their sound at all.
As to speakers and cartridges, well, the differences were OBVIOUS. There was no comparison at all between what we kids - my pals and I - could afford or scrounge together and, for example, an Electro-Voice Patrician, a Lansing Hartsfield, or (Wonder and Glory of all wonders and glories) a Bozak B310, or even between ours and many of the, less expensive but still unavailable to us, other speakers on the market. Speakers CERTAINLY made a difference.
Cartridges, too: Until the General Electric "Variable Reluctance" magnetic cartridges came along, we were all using high output (1 VOLT or more) crystal or ceramic cartridges. Then came the GE cartridge and a revolution: Its output was so low that I had to spend $13 (big bucks for a kid!) for a one-tube (12AU7, If I remember correctly) Fisher preamp to boost it up to where my amp could deal with it. As compared to what I had had before, though, it was a world of improvement.
The other parts of our systems fell, along with our electronics, into the "doesn't affect the sound" category; not because, like the electronics, they were essentially "perfect", but because being "part of the sound" wasn't their job: The turntable was just something to spin the records and, as long as it had satisfactorily low wow, flutter, and rumble, it was just fine. The tonearm was just something to hold the cartridge. And the wires? They were just wires, and what we all used (and made for ourselves) was nickel-a-foot Belden microphone cable with two-for-a-nickel cardboard-spaced "tulip" RCA connectors for hookup, and lampcord for the speaker.
Although we had no way of knowing it, a very major reason why so much of our system seemed to make so little difference was that we were listening in mono. With not even any conception of imaging, soundstaging, or ambience (other than "echo") those weren't things that we listened for, and, when they weren't there, we didn't notice their absence.
When, in 1957, stereo records (and a low-output Electro-Voice ceramic cartridge to play them) came along, a new door was opened that, frankly, most of us - even those who had "gone stereo" - didn't go through. We were too busy enjoying the glories of Left and Right and spending a now-utterly-incomprehensible amount of time listening raptly to ping pong games and marching bands, and grinning like loons as fire engines, jet fighters, and steam locomotives roared through our rooms at joyously cataclysmic volume.
In fact, though, even if we had known about the real potential of stereophonic sound, we were probably just too early in the cycle to actually pass through that "door" and take full advantage of it: Mono didn't really require "time aligned" drivers, so most speakers other than those from Tannoy didn't offer them and buyers didn't yet know enough to demand them for their stereo systems. Linn hadn't yet demonstrated undeniably that turntables could affect sound quality. Randall Research and Monster cable hadn't yet shown those who were willing to believe their ears that cables CAN be heard and DO affect overall system performance. With both imaging and soundstaging unknown, no one had even discovered yet that both imaging and soundstaging could depend on speaker placement, and "bookshelf" speaker systems were really called that because people really bought them to be placed on a bookshelf (where, as on a "boombox", they would probably be too close together to actually produce a realistic image).
Eventually, though people learned: Speakers got better; "bookshelf" speakers became "monitors" and were moved off the shelf to stands on the floor, well away from the walls; better speakers, better turntables, better tonearms, better cables, and better recording techniques helped people to hear recorded soundstage and ambience for the first time, and the result was both better recordings and better electronics.
And at that time, we finally learned what's important: Everything. It all, every element of the recording, the system that it's played on, and even the room that it's played in is important. There is no contributing link anywhere along the chain that doesn't affect the sound to at least some degree. ATTENTION TROLLS: I'm not suggesting that there is no snake oil out there, but we've finally gotten to the point where each person, with his own ears, on his own system, in his own room, can and must decide what works and what doesn't, and that's exactly where we should be. Good for Us!