Thanks for the explanation. I'm indeed familiar with the practice of Summon Fest from other gachas, but I think this all goes back to 2 things:
1. UoC were a mistake - This totally changed the way players saved and spent on banners. A lot of immediacy on the units were gone, which is bad news for a gacha game, and they really dug themselves into a hole with it. I totally understand how they're trying to circumvent this mistake with Summon Fests. This is only a problem however because of their other major fuck-up -
2. Needing 2 5* bases to make 7* units - I feel all of the problems with the current state of the game can be traced back to when this was announced. It makes pulling a single rainbow feel bad. It forces a mechanic like UoC or else players will leave. What's even more puzzling is that they already have STMRs as a thing, to easily make duplicates still valuable, yet they went this route. No doubt this has been tied to our increased overall pulls (though Gumi seems to like throwing us EX tickets instead of anything we can use intelligently), but it's really taken a toll on the game in general, especially related to limited banners. I honestly don't think anyone would have a problem with Summon Fest if all you needed was to pull the unit once. Or if Global would have lost UoC (like they were planning) if they had just removed the need for a dupe to 7*. Make it expensive, make it grindy to 7* a unit, but requiring dupes is still, I feel, the biggest mistake this game has made.