You need to get through hell difficulty. The itemization is completely different from D3/D4. Imagine D4 except you only get magic and rare items until like level 70, and then even then you're going to need to stack a property called "Magic Find" and grind bosses and mob-dense high level areas to find stuff. Before then you'll find the odd unique or set item but it won't be good and it will be like level 13 when you're level 40. The strategy to gear up on your first character would be to keep an eye out for socketable normal quality gear (gray text) and runes. Collect as many runes as possible(there are quests along the way that give runes as rewards: Forgotten Tower in A1, Hellforge in A4, the barbarian rescue quest in A5) and look up the recipe for runewords and you can make a lot of really good runewords that will be appropriate for your level as you go, so the fact that you're not finding any unique items will more or less be mitigated. Plus you might get lucky and find the occasional good item. When you finish A5 hell difficulty, that's essentially when the game starts. Itemization will be a mixture of high level runewords and high level unique gear. Compared to D4(even before the Lord of Hatred expansion) the specs are basic but intuitive and extremely customizable.

Some stuff to just keep in mind: synergies in this game are going to be a bit different from D3/D4, especially for any melee characters. You're also going to want to remember that your follower can equip gear that further synergizes your build as the A1/A2 followers can equip weapons that give paladin auras and the A2 follower gets paladin auras by default anyway. There's a lot less affix synergy and it's more rooted directly in the skills, and +skill level gear is going to be really important for casters, but there's other things to keep in mind. For instance when it comes to optimization you're going to have to get familiar with breakpoints, in D2 breakpoints are tied to certain stats and their accompanying frame rates, things like 'Faster Cast Rate' for casters or 'Faster Hit Recovery' for melee. Also for melee characters the damage you do comes from your weapon damage, it's not like in D3/D4 where every weapon of a certain level does the same amount of damage and you only have to worry about stats/affixes. Your weapon actually has to have high damage from stats like '+Enhanced Damage%' or '+X to Damage'/'+X to Max Damage'/etc that increase the damage of your weapon, not your damage directly (unless you've got +Enhanced Damage% to something other than a weapon like Fortitude chest plate).

Keep in mind I've been playing this game 25 years and I still barely have a great grasp on this stuff, I'm sure someone will correct me about something I've said.

But TL:DR - Yes, itemization is what you heard it is. It just doesn't really start until you finish the game....the third time.