I remember visiting repair shops for our aging color TV with my dad and being awed by the tables and shelves full of exotic-looking vacuum tubes, exposed CRTs, and dangerous-looking coils, and what I imagined to be the sorcerer-like skills of the man behind the counter who could divine their inner workings.
On weekends I would cajole my parents to drive me to the numerous electronic surplus stores, where I would marvel at tallboy-sized capacitors, which my father wisely prohibited me from buying.
Radio Shack was in its prime with walls covered in DIP chips and those "Electronic Project Lab" kits, of which I aspired to own the 300-in-1 version for $65 with a real breadboard and digital ICs. I vividly remember the birthday when I finally received it. I could seldom get the more complicated digital designs to work, which I've since learned was likely because breadboards are terrible for digital logic, but I was nevertheless entertained for countless hours.
Those were some of the most formative experiences of my childhood, and I too feel sad that they're becoming a thing of the past. You can open a modern electronic device and there's hardly anything in there that you can disassemble and re-use. And even if you could, the magic doesn't live there. When I was a kid, everything a device did was physically manifested in the arrangement of its parts. Now it only exists in firmware, invisible and inaccessible to the curious eye.
I suppose every generation feels nostalgia for the lost world of its childhood. But like you, I can't help but feel sad that no more children will get to experience that.