I think this card is a sleeper. The fact that it's a 4/2 that isn't Nisei MK II makes it easy to discount, but it has a lot of upsides. First of all, it's 5 cards, which is a good boost to your economy. The reveal effect is slightly annoying, and clearly only there to create a slightly artificial-feeling synergy with the Hyoubu Institute: Absolute Clarity, but you can live with it. The counter mechanic means you can pull the cards as you need them. It's not Corporate Sales Team, but it's still a significant pace advantage.
Then there's the shenanigans. As Ip87 has already pointed out, you can use this to trap the top of R&D on demand. It's not really a 'mind games' effect though, as you can fire it in the window after the runner has committed to accessing. I actually think that Jinteki trap decks would be more fun with lower variance, and this supports a move in that direction. It's more 'if I have a trap in HQ, the runner will hit it', with a consolation prize of ensuring the top of R&D is safe even if you fire speculatively and draw drunk. You can also use it to clean/trap HQ in a similar way, although given that the only place you can 'hide' agendas is on top of R&D that's often not going to be a flawless plan. I guess you could argue that's where the mind games come in. Or you could just drop an Anansi over R&D.
Another very notable synergy with this card is Political Dealings. By firing it on the runner's last click, you can stack an agenda on top of your deck to set up a reliable fast advance. This makes PolDeals a much more viable card, as you can drop it among your shell game servers and rez it only when you know the fast advance is on. This makes it comparable to a Biotic Labor, except that now the runner has to spend resources trashing it.
All of this means that Flower Sermon belongs in an entirely different deck to Nisei. Sermon gives you pace, while Nisei supports a slow, grindy game. Sermon helps with fast advance trickes while Nisei wants you to play a bunch of ice. That means that arguably, the agendas Sermon is actually up against are Fetal AI and Project Yagi-Uda. The first may be better if you're doubling down on death and don't see yourself scoring agendas that can't be never-advanced. The latter has its own, more obvious synergy with fast advance and shell games - simply being a 3/2.
This makes Flower Sermon a bit of a puzzle. It's not as good as Nisei in the Jinteki decks that are currently thought of as strong. That's why I think it's a sleeper. It will need a slightly novel deck archetype to succeed. I hope someone works it out.