Official doesn't guarantee quality, but it often tends to in comparison. One bonus of official is that most gamers I run into are aware of it. That makes using and getting buy in for games easier and more successful. Im open to unofficial too.
Official material is the tyranny of bureaucracy over creativity. The triumph of officiousness over imagination. And the victory of the stultifying dead hand of the absent rules-creator over the dynamic minds of the people at your table.
DnD Beyond pushes me to mostly use official materials, especially when it comes to PC resources. However ,as I am most often a DM, using 3rd party monsters and magic items are easy enough. I also make up plenty of my own nonsense.
I've moved on from d&d/o5e to other things like a5e/levelup but tried for years to hack o5e into a state where it might support the narrative rather than subordinate it. In a way o5e itself creates a situation where it fights attempts at using 3rd party modifications.
The big problem with unofficial stuff is that o5e lacks an underlying structural framework that can be modified to make global changes to everything it touches. Take a hypothetical shift to change how feats & asi are awarded for example... That would need between three & thirteen different versions because each class has them baked in rather than being a high level rule that just applies to characters and some classes have extra.. Any kind of third party modifications need to make some assumptions in order to build a framework that they can transplant along with their modifications and they will often make different reasonable assumptions. Mixing them results in a mess that needs to be fixed with one off edge case rules and those one off rules themselves need to get fixes to the one off problems they create. The alternative is do do it wotc style and just make a half finished bonkers system like wotc's "crafting" rules that foists the whole job of creating it onto the gm & at that point you might as well have just built it yourself.
Edit:before I switched I used quite a bit of giffyglyph's darker dungeons stuff but then I had to fight with player's looking for ways to loophole around any of the goals I had by using x or y component from it
I use both happily. Balance is over-rated in my opinion and thus is never the divining rod on whether to use or not use something. But at the same time I have absolutely no problem re-balancing something myself if I've determined that the thing in question actually is making the game less fun and could be fixed at my own table. I trust my own judgement of what my table needs to have a good time, and if that means not allowing the Lucky feat or letting the Beastmaster Ranger player have both their character and their animal companion take their own individual action, then I'll do it regardless of what the books say.
* And * not then complain that I had to make these my changes myself because WotC wouldn't do it for me. That expectation is just ridiculous.