I don't really make the assertion (unlike some people) that it was some brilliant masterpiece, but it was more enjoyable to me personally than 99.9% of games I play. As for why I enjoyed it, fairly high-quality writing, a good setting (Planescape), and pretty 2D backgrounds all play a role. The philosophical angle I'll agree on, never believed that was its strong suite, and it comes off as preachy and fairly immature when it gets too much into repeating "WHAT CAN CHANGE THE NATURE OF A MAN, BREH?!".
To me, the setting was the best part of the game, although I think the rendering style they chose was a bit meh (particularly, Carceri looked like shit). Writing had it highs and lows, and most of the characters you have to speak with through the game seem to share the same traits (a standard Sigil madness of sorts). Ravel was alright, in all her forms, and so was Dak'kon, unlike the rest of the cast you can carry with you. Examples of not so good writing characters: Anna falling in love with TNO for no real reason, Grace having no character arc at all, simply going from amused by the party to completely attached to TNO, and Morte... well, he is just a gag for most of the time, although he does have an arch that fits his persona. Nordrom, doesn't even get that, and Ignus and Vhaillor are just there to show a couple of extreme characters that are more annoying than anything else. The part with the speaking wall in the alley? That was cool. The whole Carceri/Curst? That was lame at best, and a very lazily designed portion in every aspect (those quests to get the key to the jail were really worth hundredths of thousands of xp?). The Pillar of Skulls was cool, though, but that's just but a fraction of that horrible mess.
The worst part, by far, is the ending. Once the plot unfolds you might be like "ah, that was actually pretty cool", and then you get the best ending, and nothing really matters. It's no different than the 4 buttons from DE:HR, but here you have one where everything is good, nobody dies, you become one with TTO, get sent to Baator to do what you've been doing for the past few hours of the game for an eternity, which probably would grant a beast such as TNO way more than it'd take from him. You never get to know what was it that the first incarnation did, that was so bad and regretful, even though you become one with it (and considering how much of an asshole TNO can be through the game, it must have been really bad).
Who would ever want to argue on the basis of "THIS GAME IS SHIT. PROVE ME WRONG
"
Well, you don't seem to have any arguments whatsoever, so why would anyone argue with you at all?