Alvan, firstly, and if I am mistaken, please accept my apologies in advance but I see you are from Italy and therefore, if English is not your mother tongue, then 'hats off to you for engaging in a debate in a language that is not your first!' I have nothing but respect for people who are multi lingual and that put my basic French and German to shame!
I do understand what you are saying and there appear to be two distinct points: firstly, the cesspit that social media can be. I concur entirely and find much of it mean spirited and lacking in integrity, honesty and basic kindness. Many people who are the most active and vociferous on any form of social media are the last people to say the same things when faced with a person in 'the real world'; more often than not both armchair experts and conflict avoidant in their daily lives, hence blowing off steam online. There was a psychological study done recently and statistically, the people most active on sites such as Facebook, Twitter, Instagram, Ticktok, etc, score far above the average for antisocial and psychopathic behavioural traits. Reading the study, I cannot say I was hugely surprised; narcissistic behaviour does seem to, more often than not, be the rule of the day. All generations look at the younger generation with a mix of concern and rejection of their 'new' values but I can honestly say that I do not think we have ever seen a younger generation who are so self absorbed, display confidence on social media and yet are riddled with self doubt and lacking in the ability to both stick with any task for an extended period of time and when they fail so quick to blame others. I know this is a sweeping generalisation and there are gems in the mix; however, social media and smart phones have an awful lot to answer for; the majority of it not positive.
Secondly, to answer your point about owners sounding off about the Grenadier - setting my post above to one side - I question how many of them also include speculators who are surprised and disappointed that they cannot turn a quick profit. My guess would be that there are a fair few in the mix who saw the £10k+ premium attainable on a Hardtop Defender 90 and thought they'd cash in. I'll go so far as to say I met a new owner in a carpark who told me as much - I bought it and if I don't like it, I'll flip it. I didn't have the heart to tell them that dealers have unsold cars. Needless to say, I can imagine that person being someone who rapidly turns unhappy and vocal when they cannot exit the car without the standard depreciation you expect on a new car purchase (in the UK 20% when you drive off the forecourt - prior to pandemic/post pandemic supply chain shortages and inflated used car values (all of which are rapidly on the wane for most vehicles).
If I was an owner, I'd personally enjoy driving it and ignore all the negative chatter - if you have no plans to sell, residual value is irrelevant and you cannot easily put a price or quantify the enjoyment of a new vehicle.