A thing to keep in mind is generally, forums tend to err towards the min/max levels of content. Which is where the "Never use Cure" thing comes from, because in a min/max static, it's entirely possible for Healers to co-ordinate so as to put the majority of the healing onto their oGCD skills leaving more room for pushing DPS.

However, there is far more content, as well as far more players, which will cause this playstyle to be literally impossible. Just like how the "Meta" thing for Tanks is to never use either Tank Stance nor Enmity combos, but it will be necessary for a lot of PuG groups and various dungeons and trials.

As far as WHM goes... In min/max scenarios their additional healing is unnecessary when everyone is doing mechanics nigh flawlessly all the time. But outside of that, the abundance of healing is really helpful to make up for peoples mistakes or to just give yourself some breathing room to mess up on occasion.

Lilies are... Poorly implemented. In min/max scenarios not only will your default CD's be short enough to time to the predictable incoming damage, but also you'll be trying to minimize usage of Cures to actually proc the damn things. Outside of that, it's really a case of how limited they are in generation. ONLY being from casting Cure I/II (With additional Secret of the Lilies II also only proccing off critical Cure I/II...) that makes them really kind of bad to play around. Since, given the plethora of other skills you have, you tend to want to minimize your use of Cure I/II anyway in favour of just using your oGCD's, Regen, Medica's and Cure III with Cure I/II being just the last resort for bringing someone's health up.

However, this is merely in the current expansion. No doubt that come Shadowbringers, there will be some changes to WHM and likely Lilies that will help alleviate some of these concerns and ideally make Lilies be more useful to the point of wanting to play around them (For example, hopefully they're not still tied to Cure I/II only...)