And? We use that in SSDs for example, not in transistors (quantum tunneling for electrons) - it's the effect without which having SSDs wouldn't be possible. SSD cells also are already perfect size and can't get any smaller for years now, or the effect would be too large to keep any data in them reliably. Same situation with RAM cells (including cache) components and also with analogue bits that are in CPU (for example) - they don't scale down at all now. In other words, we use some quantum effects, in a very controlled manner, which would quickly spiral out of control if components got any smaller - that's how quantum physics work, the smaller you get the more uncertainty you get and then less you can control it, as it becomes more and more random (and you get whole probabilities then instead of certainty). That might work for quantum computers but definitely won't for classical binary ones.
And yet most components can't and don't get smaller anymore. For years now. AMD engineers said that in interview about Ryzen 9000, data from chips manufacturers show this, engineers from other companies designing components say that, articles about electronics have been showing that with photos for years now etc. - this is all well documented and a known thing, not open for discussion. What changes is just exact design of transistors, accuracy of creating them, materials used in it, spaces between transistors (mostly done for better heat dissipation) etc. Not actual sizes of the components - thickness of these components can already be counted in number of atoms used as is.