Interesting point. But, shiny new ships were there for long. For example, it is officially stated that at least one T45 has long been in extended readiness because of lack of crew. Shiny new kits, which should have improved the retention rate, was NOT USED for years. This has nothing to do with its propulsion issue. The other 4 or 5 T45 was always used.
Please do not get me wrong. I am NOT against current 5 T31 and 8 T26 building. Just saying T32 is NOT in hurry. RN will find big difficulty to man all the new T31s and T26s. Even though they require relatively less man power, RN can use them in much more high-tempo than current T23 fleet, because they are new and not needing intensive maintenance.
And this will put big burden on crew daily life. Less time at home. So, more crew is needed to "over crew" all the new ships.
When these assets become a bit "tired" (say, around 2035-2040), then longer maintenance will be needed, and it will allow less tension on crew. It is exactly at this moment, RN needs T32 (or more T26 or T83).
Not now.
And now, RN has many many things to invest. Ammo and man-power, ammo and man-power, and ammo and man-power, and then drones, ASMs, BMDs etc...