As for the seeds I agree. It's like eating kiwi seeds.
Mangosteen is great! No idea why the author had so much hate.
Durian though ... well I've tried it about 7-8 times and I get that it "tastes" good but I still don't get it. For example in Singapore there is a chain of cream puff stores that carry durian and vanilla cream puffs. To my "unrefined" palette they taste 95% the same but one stinks so if I was to go again I'd choose the vanilla that doesn't stink vs the durian that does. I'm sure I'll try them again but I suspect my reaction will be the same. Tastes fine (like vanilla custard) but why put up with the stink when I can just have vanilla custard.
That said, last summer when I was in Malaysia was the first time the smell started not being so repelling so (a) I'm getting used to it (b) they were in season (c) like the cat virus they've reprogramed my brain :P
Our experience is vastly different!
While not a fan of dragon fruit, I do eat it relatively often as my wife loves it. We usually buy pre-peeled pack at the super market when we visit.
For me it is definitely sweet. Not 'extremely' but it's definitely sweeter than a good banana or royal grape. Definitely not bland at all. I don't think I've had a non-sweet version in any of the countries you listed.
Edit: I just had a thought. I always eat Purple dragon fruit, not the white one. Maybe that's the difference.
Anyway, I'll keep trying dragon fruit hoping for a sweet one.
I think at the moment my favorite fruit I've had in SE Asia is cherimoya and I'm surprised they are not way more popular as they are so dang delicious! It's like someone made an apple + orange creamsicle fruit
It's one of my wifes favourite fruits, but we can't find good one in Singapore.
To choose a dragonfruit, pick the ones where the "leaves"/"tips" aren't dried out, feel heavy/full and slightly firm.
Keep in mind that there are over 200 varieties of Durian - some are even red inside, some sweet, some more pungent than others, different notes and textures. The best for me is Musang King variety in Malaysia, esp. when they get a slight alcohol after taste.
There are different places you can get durian puffs where the filling is basically pure durian. Of course, unless you love durian you're not going to appreciate them.
A lot of people have heard by now that there are many interesting types of bananas overseas, but they don't travel well enough to reach other countries. The same goes for other fruits. I remember once reading about a durian that has nearly none of the repulsive flavours, but they just aren't common enough to send away from local markets (I think it was in Malaysia).
On the other hand though some fruits freeze decently well, durian is one of those. Especially if you're cooking with it the peeled pieces are great.
If you can pick your own, though, they're in my experience pretty avoidable: go for ones that are purple, not black, and avoid any that have traces of yellow leaking from the top.
I've been trying to find a good one in the states, so far no luck. I've only tried ones with the red flesh. The ones I had weren't bad, they were just flavorless. Not sweet at all. Kind of refreshing, but nothing special.
Mangosteen is so far from its depiction---"to eat a pile of mangosteens is an exercise in disappointment"---that I wonder what kind of pile the author ate. In the US, imported mangosteens can run $20 a pound, so getting a few bad ones would be a disappointment. I suppose many vendors would issue a refund for the bad ones. But in Thailand a pile of mangosteens is so cheap that you wouldn't bother. They are exquisite, almost the fruit equivalent of ice cream (they taste better chilled). It's no wonder they call it the queen of fruits.
Durian likewise deserves its designation as king of fruits. Most people, myself included, are repulsed on the first encounter. But if you can get over the initial shock, you will enjoy the most flavorful fruit with custard-like texture. Its flavor can be described as a combination of many other fruit flavors with a complexity only matched by good coffee and dark chocolate.
Jackfruit is cheap and abundant in Mexican and Asian supermarkets in the US. The trouble is peeling and finishing a whole one. Some stores may sell wrapped pieces if you just want a taste. But if you have some guests and time to work with gloves and a knife, eating a whole jackfruit is a memorable experience.