Someone on our table was turned away at last night’s gala night for not being in a dinner jacket or dark suit. So there is still enforcement, but outside the gala nights the requirement is merely for smart attire meaning a proper shirt and no shorts, jeans etc - so standards are already sufficiently relaxed not to hinder anyone travelling without a jacket. On the two gala nights out of seven you just eat at Kings Court, or in your cabin.
After the pandemic, being overly fussy about dress codes seems an anachronism, and the new Cunard approach of being fairly relaxed most of the time but still with a handful of ‘dressing up’ nights is probably a decent balance for modern times.