For most of the reasons people shit on XIII they praise X. Both have a lot of the same problems from being too linear to a terrible plot and characters. Not to mention the godfucking awful Nomura art design strikes again. The only good design he ever put out is when someone told him to stop at some point. Like FF7 and Xenoblade 2 (he designed Jin and Malos)
Nah mate, you gotta understand that there's more to the arguments than just 'one is linear, so is the other, therefore they're both bad'. Almost every complaint boiled down to the idea that the problems with FFXIII went way too far in the wrong direction.
FFX is linear, with side paths and exploration and room to do shit on the side like minigames and side questing.
FFXIII might as well have been on rails. Outside of chapter 11 there was almost no side content or exploration or minigames or quests. Outside of one small bit of the total length, the game might as well have been an on-rails RPG both for its world exploration, character choices, and even level progression (the Crystarium).
FFX is a linear game that balances out its linearity with side content. IT balanced it with well explored characters and a more realized world. It balanced it with so many other features and distractions. FFXIII went WAY too far off the deep end with making the game way too linear with little to nothing to do on the side. The difference is the matter of degree, and that matters a lot. you seem to agree with this point yet still seem to think that people are wrong to criticize XIII but praise X despite them havining many similar design aspects.
The reality is, one of them does it well. The other does not. I also think you're just hilariously wrong about the writing and characters not being good in X. I felt that the writing and characters were some of the best parts of X, but in XIII you needed to read an in-game encyclopedia to even know half of what the fuck was going on at any given time. There's depth in world-building, then there's homework.
My Console Library:
PS4, PS3, PS2, PS1, WiiU, Wii, GCN, N64 SNES, XBO, 360
3DS, DS, GBA, Vita, PSP, Android
Top 6 this generation:
Bloodborne, Sekiro: Shadows Die Twice, God of War, The Legend of Zelda: Breath of the Wild, Dark Souls III, Red Dead Redemption II, Rock Band 4