One thing I often think about is a description of the distribution of job-quality as being fat-tailed[1]. That is, the 95th percentile job is a lot better than a median job and, in particular, is a lot better than if job quality were normally distributed. The referenced piece describes some strategies for looking for outliers in a fat-tailed distribution (e.g. the best jobs). If you agree that job-quality is fat-tailed, you should be wary of the phrase ‘as good as the best’ because there is a lot of difference in the tail. But, it is conceivable that your firm gives you a job which suits you to a similar amount than what you might get at similarly sized companies with similar businesses.
If your job is currently outlier-good, you have a high chance of ending up with something worse if you move to a random job, and even if you know what sort of things you like about it and try to find things you think you’ll want, there might be things that you like but don’t realise until you move and so fail to take into account when looking for other jobs.
One thing that might be useful to you is trying to figure out how your job compares to what other jobs could be. I think the only real way to do this is talking to people you know at other companies, ideally people who have worked at multiple places and have been around long enough wherever they work to see more of the inner workings. If you don’t know such people then maybe you’d be able to meet them socially at parties or conferences or something. I think things online will be written either by companies (mostly emphasizing good parts) or by people with unrepresentative opinions and so you will likely not get the most realistic picture.
There are some other things you could do, e.g. talking to people within your own firm who have worked in many places but stuck there – why did they leave places before, why do they like the current place, what do they not like about it? Or looking at some statistics like attrition (and do people not leave because they are happy or because they are e.g. sitting around waiting for an IPO?). Another thing you could look for is people who leave and then come back (which would likely also be an option for you too if you left – don’t burn bridges and if they liked you before they would presumably be happier to hire someone they already have a good read on and who better understands the business than a typical external hire). If people leave and then return, maybe they left for personal reasons unrelated to the job (e.g. a spouse moving to a distant city for work and then returning), or maybe they left for other companies, and thought that the previous place was a better option. Or maybe they went to pursue something like being a farmer or a carpenter or retired or whatever and decided it wasn’t for them and returned.
[1] https://www.benkuhn.net/outliers/