In my opinion, you would have to use dragon wish at the right moment. Your opponent will see it coming and maybe use ranger or N or delinquent to disrupt you.
If you can get the setup going then the payoff is great though. High risk high reward.
Solgaleo involves less risk, but not everyone is crazy about GXs or EXs.
Just a quick list of things that Solgaleo and Dragonair can setup:
Gigalith SM (difficult)
Solgaleo is just better at this job than dragonair. But I'm the type of person that enjoys playing non EXs more so I would try to flood the field with energy with dragonair just for fun.
I wouldn't be so quick to call it a really good card. Use it if you enjoy using it. I know i make a lot of bad deck ideas (Past friends Chandelure, Pangoro BKP/ Diance EX, Ho Oh EX) but I love playing these decks because they are different!
I would definitely use dragonair over Solgaleo because it makes you think more about your engine and setup. Seeing potential in obvious cards that are good like Tauros GX and Lurantis GX is not as impressive as seeing a potentially bad deck idea actually win matches.
Build your dragonair deck and post it. It may not be the best idea, but at the end of the day you can think outside the box and level up your deck building skills in the process.