Anyone else feel like this card was a massive missed opportunity with no time to shine?

Additions in Kaladesh block such as Harnessed Lightning and Dynavolt Tower to break up the meld for cheap, Ajani, Noxious Gearhulk and Intimations to kill it post-meld, life sure got worse for the already lofty pipe dream of Brisela, Voice of Nightmares. Gisela by herself is still very playable, albeit in the zone of most removal available, but Bruna has gone from fringe to barely fringe. Maybe its just that reanimation decks fell flat on their faces, or angel ramp wasn't packing enough consistency and instant speed removal to deal with Vehicles, I'm just a little sad that such a sweet finisher never got its chance to shine. Unless Amonkhet massively shifts the meta away from Vehicle speed aggro, Dynavolt and Harnessed Lightning, I don't see that ever changing.

aren't card discussions supposed to be about interesting cards?

I'm trying a orzhov angels control deck built around Brisela. To make you understand the focus on it, i just say i have 1 copy of Diabolic Tutor and Planar Bridge. Maybe the deck could be better without such cards and Bruna, but it works fairly well also against aggro, having tons of removals and also enough lifegain.
It's not very difficult to avoid removals against Brisela. They are not many and when you know which kind of deck your opponent is using it's also easier. Planar Bridge could be slow and bad in particular situations, but if you can slow down your opponent with removals it is worth it in this deck. For fun i tried it in superfriends, ramp and other kind of decks, but never worth it. Not sure about this deck, but it's better here than other decks. You can play your threats at opponent's eot, especially brisela if you are sure that survives, otherwise just take all your pws and force your opponent to tap out.
In general i would say that Brisela is not worth to consider in your deck, but this list is funny, with lot of control and some tutors.

Brisela is powerful and can definitely immediately lock a game. Her problem? 7 mana, and you need her pieces in play immediately.

I have played her in various shells, none of which perform well in the current meta. Ramp gets aggroed, Orzhov can't put up pressure well enough. Also most decks can't run enough Humans for Bruna to get something back reliably.

Clearly, someone hasn't realised the true power behind going Bruna into Exquisite archangel

Angel ramp isn't terrible it just suffers from the age old problem of "why aren't i just playing normal ramp instead?"

At least Dec in stone has lost a lot of usage so it's way less likely gisela gets exiled, i'd say that's more relevant than ajani and noxious who aren't as popular as that was back in the day

It's a very strong pay-off, the setup is just too difficult however. Bruna and Gisela are rare and mythic respectively and aren't too great on their own (bruna is too expensive for the unreliable payoff and Gisela dies to every piece of removal played)

I feel like you contradict yourself a bit - Harnessed Lightning, Dynavolt Tower etc do break up the meld, but they also specifically target Gisela, which you said is still playable (?).

I think the main problem with Brisela is what Joly said. Bruna is rare and Gisela is mythic. That's a roughly 66% chance of drawing Bruna without Gisela. If we could run more Brunas and Giselas, then even getting Brisela eaten post-meld isn't too bad, since you could always play another Bruna. As it is you could still play an angels & humans deck, but the star player would (ironically) be Bruna instead of Gisela. For Brisela to be better, we need: better access to Bruna and Gisela. If we can't run more copies, then something like Thalia's Lancers to tutor for them.

I'm still going to tune a Brisela deck someday since Bruna is still my favourite card, but right now working on other decks.

PS: vehicles aren't too bad, you're in white so you have Fragmentize, and if you're playing ramp you also have Reclamation Sage.

I feel like this is a pretty good summation.

In regards to Bruna herself. I feel like her biggest issues are her cost, and ironically, her on cast trigger.

Many of the decks running a glut of humans that want to be bringing them back aren't going to be wanting to pay 7 mana for that effect. Being 7 mana the most obvious way to use the card would be to cheat it out with reanimation spells, but because the trigger is on cast and not ETB this idea falls flat on its face.

As such we are mostly forced into hard casting it for 7 mana, which isn't terrible, but isn't great either.

Not being able to effectively cast Bruna from the GY just furthers the rarity issues it has, since we can't use self-mill as effectively as a means of digging for it (well, we can with cards like Grapple with the Past, but that is still less mana and tempo efficient than just being able to reanimate it would be).

Not really. Gisela has always been the most vulnerable part of the combo, but she is the better of the 2 cards by a wide margin. There's two factors I look at in a cards "power level", which are up-front power, and it's current value/worth in the meta. Gisela is often called mini-Baneslayer Angel, which is an accurate assessment of her above-curve stats and keywords. If she isn't dealt with immediately, she cripples aggro mirrors as a curve topper or clocks slower opponents. Is her power reliant on the deck that runs her by herself? No, she's self-contained. However...

Is her value lessened by an increase in removal spells currently run that hit her? Yes. Harnessed Lightning and Dynavolt tower are very common cards to see atm, with one of them being a sure-fire guarantee in any deck you see running Red (which I shouldn't have to tell anyone, is the most popular colour currently). Because of this, the likelihood of Gisela getting shot down is much higher than before. Always Watching used to be the main card that could get around this, but it is not run that often due to its speed/worth to better aggro decks like Vehicles that can just swing over the top of pumped weenies. So you see, she isn't any less powerful than before, but in my eyes much less appealing if the likelihood of paying 4 mana to whiff is much higher than before.