I’m not sure that comparison makes much sense. By the time CRTs were phased out, demand was down to almost nothing and what little existed was confined to the extreme budget market. While I don’t have industry insights or anything I don’t think demand for DDR4 is anywhere near the bottom yet, and the remaining demand is centered on premium product (nobody running cheap DDR4 is upgrading). In a more normal market would be more than enough to justify continued production for several more years.
DDR4 production is likely still quite profitable, just not drowning-in-money AI-bubble profitable. If smaller foundries existed they’d be happy to take up the business.
Maybe really what needs to happen is some busting up of the giants…
There is a minimum amount of production volume for it to fit the price equation. If the market doesn't have that demand, it is fundamentally no different to CRT.
Otherwise they could continue to make DDR4 at a higher cost and sold at a higher price to which people will complain price fixing again.