Are Macros bad?

I'm currently using mouse over macros for my healing spells for conjurer, but I've heard whisperings that using macros is bad. Is it not a good idea to use mouse over macros for healing?

Those should be fine. Most of the problems with macros come from other usage, such as:

1. putting multiple actions in a single macro, which requires lengthy delays between the actions, making it less efficient than manually performing the actions
2. using macros to spam chat
3. using third-party macro programs rather than the in-game tools

Macros are (in general) unreliable in this game.
Due to the way skills queue, macros can often misfire or fail to go off entirely. Text macros are usually pretty safe though, but when people say "they're bad" this is what they mean. That they don't normally work right in FF14.

There are macros that are alright. Target and focus target macros, gearset macros, place-target macros such as for healer bubbles, UI toggle macros, volume macros, shirk macros for tank swaps, macros that give buffs to your co-tank, tether macros for dragon sight or cover. I use macros to remove autofacetarget when healing but to re-enable it when doing damage, so I can turn away and still heal.

Using macros for GCDs or chains of GCDs and off-globals tends to cause problems sometimes, but if they help you with a disability or you find they are what you need to enjoy the game, you can still use them. Just be aware of the problems with them and acknowledge the downsides, like how the macro might occasionally not trigger some of the actions or how the delays between attacks may be longer than if you pressed them yourself, making it a damage loss.

Using mouseover macros to heal will delay the starts of your heals by about 0.2s; but if this is the only control scheme that lets you reliably cast all your heals on all the correct people, then that is worth the slight drift. There are three generally fine use cases for combat macros:

• Mouseover heals/buffs
• Fixed-target or mouseover party member actions (e.g., tank always using Shirk on <2>, or DRG always using Dragon Sight on <4> in a light party)
• Ground AoE placement without having to fiddle with the ground target cursor

Other combat macros are generally considered bad because they cause this to happen:
https://i.imgur.com/NwflNWc.png

This drift is a result of macros not participating in the action queue. They have to be pressed after all GCD and animation locks are released, which means you'll always activate them at least 0.2s after you could have activated them with the raw action button. For attacks this results in many lost GCDs over the course of a fight. A healer will also lose GCDs over the course of a fight from mouseover healing, but as I said before, this is generally worth it if it lets you heal the right people without hesitating or wasting heals on the wrong people.