The catch is that it seems the MC's arrival is what finally pushed Debbie to DO something about her long simmering crush. Now that Debbie is in motion, the MC walking away won't defuse things. The last chance to defuse things was when Katie requested the beach house for the sleepover. Pulling the MC out of the picture now just makes it that much easier for Debbie to work her legendary ninja seduction skills on Lily unimpeded.
If the MC is only interested in Katie, then what happens to Debbie and Lily can be safely left off screen. But if the MC is only interested in Debbie or in Lily, ignoring the issue is a glaring omission.
I'm largely in agreement with you, but I do think there are two important things to consider here.
First, yes, a big foursome scene is clearly fan service, but not all fan service is bad. In this case, the lingering tension between the MC and Katie's posse has been going on for ages. It was going to have to be brought to a proper boil at some point and this does feel like an appropriate point.
It always sucks to see resources thrown at an option you personally have no interest in, but other people have different tastes. I mean personally, Katie falls extremely flat as a romance option so I'd rather she was sidelined to a supporting character role, but that's hardly fair to all her devout fans (who far outnumber me!). In this particular case I think the interest in the orgy more than justified the time spent on the episode.
The second issue is that, precisely because the MC has been able to fuck each of the girls solo, we eventually need some sort of reckoning to sort out where the four will stand once the MC's liaisons finally out. Given this is a porn game, a big sex scene is a better place to do that than most options.
Unfortunately, it sounds like Episode 19 has not worked out all the resolutions yet, at least for certain paths. The MC has very limited options to prevent Debbie from getting with Lily, and a lot of those efforts are presented in very poor light. On top of that, the episode ends before we actually learn where everyone stands the next day.
That is a serious problem that does undercut the time and effort spent on the blockbuster. I understand the devs faced real world hurdles and didn't want to stonewall the large majority of the fanbase who weren't going to see the missing branches in the first place, but I think it was a mistake to release the episode in this state. At the very least, put some sort of place-holder dialog explaining that a given version of the scene isn't finished yet rather than figuratively cutting to black and assuming we'll work out why our initial fears might not be justified.
There's absolutely nothing wrong with the majority of the fan getting a big, fun payoff for a long running sub-plot. But at the same time, I wish it hadn't treated the minority that opted out of that payoff as a literal afterthought. I know it was never intended that way, but it's hard not to feel that way when we get a high-stakes cliffhanger and everyone else goes home satisfied (or never came to the theater at all). We can't read the devs' minds, after all.
