My gaming group was, for many years, a high-op 3.5 group. We switched to 5e last fall due to a new group composition: only 1 player from the die-hards stuck around (aside from me, the DM), everyone else got babies or stupid jobs or moved. The other 5 players (who rotate in and out due to schedules, usually about 3-4 players at the table ) are from different backgrounds: one is a 2E Grognard, one is a 4E rookie, one is a 3.5 veteran who is usually too high to recall having played before... You get the picture.
We are all liking 5e, for various reasons. The simplification of the system is intense, from the perspective of a DM who would routinely spend weeks crafting major NPCs or boss fights in 3.5. From the perspective of the players with less experience, it is extremely approachable. It has enough baked in traditions from the other versions that it is easy for anyone to pick up if they have had the slightest exposure to a DnD game. I would characterize the ideology of game design as 'elegant'. Not as deep as 3.5, but certainly easier on the eye and brain than the jerry-rigged, cancerous hatchet job of revisions, updates, erratum and house rules that 3.5 became ( I say that with deepest affection for all things 3.5, except you, Toughness. Fuck you.)
One of the major features that I am enjoying as a DM is the ability to plug things in on the fly. A system that is simple is easy to attach things to. Magic items, monsters, settings, spells, are all pretty easy to adapt from the myriad 3.5 and 2E sources I have in my library.
I'm a Monty Haul/Gygaxian hybrid DM, so the game is never going to feel all that "simple" for myself or my players: they're going to get tons of loot and items and bonus feats and boons and yadda yadda, and then they're going to die or have their gender switched or their limbs removed or be cursed into being a were-sandwich or what-have-you, so the lack of 50 sourcebooks to meticulously plot out their advancement to level 20 doesn't register.
As far as the ability to customize your character from the player's perspective, I feel that the background aspect of the character creation does a great job of that, especially with the variants or write-your-own version. Feats are neat and powerful (except the Grappler one, what the fuck) enough to be a difficult choice most of the time, and the classes feel different enough that there isn't really a "right" answer for a given role.
A suggestion that I have for you as a 3.5 player is to use an unusual character concept and then try to build it using the 5e mechanics. Multiclassing is sweet, finally, instead of obligatory or ridiculous, and there's a wide variety of things that can be easily refluffed to fit a given genre (for instance, a space pirate in my game uses Eldritch Blast as his laser gun).
