I'm not sure how many hours it took me to platinum Mad Max, but my PSNprofile says it was three weeks and four days.

A few hours after work during the week and most of the day during weekends. 

Like you said, I usually get all the stuff I feel like and then finish the story mode on most games, but it's nice to get a platinum once in a while too.

GTA V had one like that too. Joke trophies and Easter egg trophies are fun.

I think I finished the game at around 35 hours, so I feel like it would have taken another 10-20 hours to get the Platinum.

I only tend to get Platinums if they're really easy or if it's from a franchise I really like (like R&C or Uncharted)

You walk over the street, get hit by a car and get the ''Hit and run'' trophy.
You then recovers and walk over the street, you get the ''One foot over the road''
You then bump into a AI, you get the ''Watch out jackass'' trophy.*
You stare at the sun, you get the ''The temporal blindness''
You waited for the traffic sign to give you green light ''Patient driver'' 
You ran on red light, you get the ''Red ring of death''
You stepped upon a newspaper ''You stepped in shit''

Trophies were made to manipulate and create addictions for ensured profit's, by the time you felt you have worked to hard for these ''scores'' you will always be forced to stick with that platform or incapable of moving onto other things, or else you loose everything you have Achieved... Since it is a tool, like pretty much every item that are being sold, these things will reach no end and will always evovle and test boundaries to see if it's accepted by the crowd. People are even depriving themselves for fun due for this type of stuff, which they did admit. Making it easier to get trophies and achievement's in general, will encourage them to feel like winners and they are hooked. 

Look at smoking, it's pretty much just crap but due for the nicotine, people are pretty much forced to continue to buy that shit because they were stupid enough to begin and later regret, trying to fill that regret with another smoke...
Humans have lost it's true nature and replaced it with a feeling of emptyness, a void people try to fill with shit that cost tons, and for what? Absolutely nothing. Some people get addicted to drugs, others to shopping or in general materialism, because it makes them feel better, for a short while. 

Also, don't forget that kids these days ends up at therapy cause they can't be away from their phones one single minute without being forced to or if they are a sleep. 

Addiction+Materialism+Capitalism= $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$, it can't work without either of them

Absolutely. Games like Bloodborne do it right and others i.e Uncharted or The Last of Us are just ridiculous imo. I don't bother with checkbox style achievements/trophies.

Yes but at the end they are pointless and won't get you anything except for some self acomplishment. I usually try to get the most I can but if I have to waste 20+ hours of my life in one single stupid trophy better to move onto another game.

So how long before trophies become either giveaways or totally impossible to achieve with no middle ground?

How a dev implements trophies in their games should be a major point in game reviews.