A website like wowhead but for FF14

[Enla]

Nothing as good. FFXIV has pretty terrible community resources if you compare it to other big games. Maybe the Japanese have good sites, I don't know.

I think the issue is that nothing is centralized. The individual parts are all amazing and work really well, Garlond Tools is a life saver as is SkyWatcher and all the community driven guides on singular pieces of content, but no one group is interested in consolidating. Which I can't really blame them for recently as a LOT of it is behind discord servers like The Balance and copying everything to an actual website would be a pain. That said it's never been much of an issue in my experience because the tools that ARE there aren't too hard to find and are usually just a google search away.

That said OP:
The Balance Discord - Your one stop shop for progression and class mechanics.
Garland Tools - Item database. Has several other functions but it's absolutely a life saver.
Consolegameswiki/gamerescape/lodestone - Jeeqbit and Anhra covered these.
Skywatcher - Tells you the weather in game. Very useful for fishing.
FFXIVCollect - VERY useful for when you're hunting down specific titles and items.
LuckyBancho - Keeps tallies on server populations and achievements across said servers. Not as useful day to day but very useful if you want to check the health of any given server.
Youtube - Check out MrHappy and MTQ for encounter mechanics. Both of them have videos going back to ARR and both are really good about staying on top of current content. MTQ takes longer but her guides are usually more concise, but MrHappy is usually a good quick alternative these days.
Eorzeacollection - Glamour for days.

Everything else you can generally find via the Reddit as I can almost guarantee someone has made a gigantic google doc for whatever you're curious about.