CM
100% absolutely well said!
I have met loads of people who slag off the IMC Rating, and to my best recollection each and every one of them had no experience on which to base that attitude.
I do some 150hrs/year, in a modern airways-equipped aircraft in which absolutely everything works, loads of it IFR, and that's more than good enough for the privileges of either the IMCR or the IR, in UK weather.
Now, if somebody said something like "the standard of IMCR instruction is often poor, and most pilots have difficulty getting their hands on a suitable aircraft" that might be something worth discussing. But one could say the same about the basic PPL, actual training versus the theoretical privileges, and we would start yet another thread on the subject....
Regarding the original question of a go/no go decision, caution/safety is one of those areas where one is always on a hiding to nothing ("human life is priceless, and any speed kills, hence speed limits should be zero ....") however I don't generally go along with the often patronising attitude of so many GA elders, exemplified by statements such as "if there is doubt, there is no doubt". If one has had a certain training, one has an aircraft which functions adequately for the task, and the conditions are within all technical limits, and there are fallback options (enough reserve fuel to get to a realistic alternate) then one may as well do the flight.
The alternative is a gradual loss of confidence, ending in the ending of one's flying and wasting of the £5k-£10k (plus a huge amount of time and hassle) one has thrown at doing the PPL. This is what happens to some 90%+ of PPL holders, before their first renewal comes up after two years.
A professional pilot doesn't say "I don't really feel like flying now, but I can't put my finger on why". He has had a higher level of training and flies a much more capable aircraft, so his go/no go decision is made at a higher level of technical challenge, but fundamentally there is no difference.
(Passengers are a separate issue; often a backup plan is a huge hassle because they cannot be dumped at some hotel for the night if the weather closes in, but that is "PPL flying"...)
It is because the training is so inadequate that we get a PPL, with legal daylight VMC privileges down to 3k vis, and then we are told to not fly if the conditions look ever so slightly iffy.
This is missing the objective which is to learn the skills one has paid for, and make use of them.