Yes manufacturers can produce light bikes today, sports bikes and enduro type bikes prove that.
What bugged / perplexed me was retro bikes. It came to a head when my Dad who sold his Hinckley Bonnie due to it getting too heavy for him was amazed how light my ‘68 Bonnie felt. He liked it so much I have t seen it since…!
But having pondered it a bit, I’ve concluded it all comes down to money. I think the manufacturers could easily build much lighter retro bikes, but that would require materials and effort that would bump up the price, and folk wouldn’t buy them.
Modern bikes do have a lot more stuff in them, so manufactures have actually reduced weight in order to keep the weight where it is with the added stuff.
Manufacturers work to targets. Target power, target weight, target sales price, target manufacturing cost, etc. To do this they find out what the market really demands in terms of that balance, then make something which fits the requirements.
Folk are often keen to talk about what they want in a bike… but when it puts the price up, the conversation changes…