My reservations on sim vs real flying is the artificial halo you can build around your true capability and readiness. In the universe championed by some air officers the aircrew stay sharp in the box and the support personnel practice their skills on training rigs, CBT, simulated workloads and time-coordinated maintenance.
But life isn't fair.
The sickening madness in not training as you fight will leave whole swathes of essential support elements unbloodied and untested. Steady-state manning of engineers and other support personnel will be chipped away in peacetime in the hope that it will be 'just like the modelling' come the surge to a near-peer conflict. On-the-job training and experience will atrophy, yet a state board of 'serviceable' (but not flown recently) aircraft will give a veneer of skills that may not prove to be much, come the inevitable. Chiselers and sycophants will keep their careers alive by papering over the cracks declaring readiness states and capabilities that would evaporate if actually tested. Aircraft with low hours and low cycle rate but increasing age will diverge from maintenance predictions. Latent failures that only manifest themselves during high cycle rates will remain latent and design issues will be overcome by the slack of peacetime ops, rather than designed-out during the early years.
A few years ago the then AOC 1Gp was struck dumb when it transpired that a deployed squadron had zero experience of an actual engine change. Phoning around the usual suspects revealed nobody currently in the RAF had completed one either. What should have been a routine event became a major hurdle, with contracts let and 'experience' bought in from the civilian world. During the engine change itself some impact damage was noted on one of the highly machined mating parts on the aircraft's engine mounts and wheel of faff was prodded along by the long-screwdriver of disbelief... "just how did we get here?".
As a parting shot from an ex-T&E chap I can only nod towards the recent F-35A accident where the 'aviate' bit for the pilot saw him make the correct final flying control input - full aft stick and hold, whilst selecting AB, to throw away a bad approach. It is what the book said to do and it also works just fine in the sim. Regrettably he became the accidental test pilot of that part of the flying control law envelope. Nobody has found a way to make a simulator truly representative; errors and omissions in FCS logic remain dormant until found and nobody consciously designs FCS flaws into the sim.
We need synthetics to cover the tactics and procedures that we may not be able to practice outside of a real shooting war. Using synthetics to save the last few % of through-life costs of a complicated weapon system is sheer folly. Those of us that preached from this book are easily dismissed as yesterday's men, but the future will not be so forgiving.