Last Played 2012 - Do I Need Windower Still?

Do I still need windower? Or is the default UI good now?
I used to use windower, mainly for party TP and better buff/debuff icons, timers on buffs/debuffs, utsusemi shadow counter and a few other things.

Most of the stuff you're describing has been implemented in game since 2012. Main benefit for Windower is really for addons. Here's a quick list of some in-game commands they've added:

/statustimer on - shows you how long buffs and debuffs are going to last. The icons will flash when they're about to wear off, too.
/statusparty on - shows you buffs/debuffs a party member you're targeting has
/partyinfo showtp on - shows TP of party members
/lockstyleset # - keeps the visual display of armor sets (and weapons, if they're the same type) you define in the new equipment slots. This is extremely flexible, you can dress up in any gear you own and can equip on at least 1 job (ex: Level 1 SMN wearing Koenig from your level 99 PLD).
/lockstyle [on/off] - turns on/off lockstyle; "on" simply sets whatever you're currently wearing
/areaeffect on - activates a visual effect when you're selecting targets of AoE actions, so you can see what you'll hit
/hidetrust on - hides trusts from players outside your party
/itemsearch "Item Name" - checks your inventory for gear
/timestamp [on/off/min/sec] - puts a timestamp in the log, either minutes or seconds
/lastsynth - Repeats your last synthesis recipe
/localsettings blureffect off - turns off Avatar glows
/mutebgm - mutes in-game music until you zone or type it again
/mutese - mutes in-game sound effects until you zone or type it again
/wardrobe and /wardrobe2 - extra inventories for you to keep equipment in, which you can equip despite being stored. Wardrobe 3 and 4 exist but you have to pay extra real dollars for them monthly.
/mh2 - you get another Mog Safe for talking to your Moogle in your home nation after doing the MH exit quests
/ls2 - you can equip another linkshell
/mount "Name" - a quest in Upper Jeuno gives you "mounts", which you can call upon in most outdoor places. Default mount is Raptor, but you can get more through quests and login points

And here are a few Windower addons or features that are popular:
Gearswap: Automates equipment changes and allows for other useful things. If you used Spellcast before, it's rather similar in purpose.
FindAll: Simplifies searching between your character and mules. Unlike /itemsearch, you don't have to type the full name, and checks storage systems like Porter Moogle, as well as mules.
Enternity: Automates pressing "enter" in cutscenes and stuff, so you can go make a sandwich or whatever while Lilisette talks to Cait Sith.
Shortcuts: Allows you to use abilities/spells/WSs/etc through shorthand, like typing //c4 will cast Cure IV.
Aliases: Essentially Shortcuts, but you can define what they are, so you can make custom shorthand commands, like say //bwa to cast Barwater.

Also there is a shadow counter now days its always on. Only thing is once you have 5 or more it just says 5+ till you drop below 5.

Also for the better buff/debuff icons you don't need windower and it never included them that I recall. Also Jeanpaul made a much better set in the last few years.