At its best, this is a Monastery Mentor combo deck. The plays it can make when it untaps with a Mentor are truly filthy: kill a creature, make multiple tokens, and then do it again the next turn (which unfortunately kills your opponent, so you don’t get to do it for a third turn). This isn’t just realistic, it’s the norm. Monastery Mentor is Jeskai Ascendancy plus Hordeling Outburst in a single card (if you ignore its vulnerability).
The second-best thing this deck has going on is drawing three cards for 1 mana (yes, Ancestral is the second-best thing going on). The same things that prowess wants—lots of cheap spells—also work to fuel delve extremely quickly, making Treasure Cruise feel like it did in Modern and Legacy. Toss in the 16 fetchlands and 4 Jaces you want to play anyway, and the deck is so good at delving that it can afford to play Murderous Cuts on top of 4 Cruises.
Strategically, this is essentially a control deck looking to go long and win on the back of drawing lots of cards. While it can win early with Mentor, realistically its early creatures usually die and the deck’s plan is to outdraw the opponent and eventually stick an efficient threat.
This deck is more linear and as a result less flexible than your typical Jeskai deck. It can’t go aggressive or burn opponents out, and is more focused on its own game plan than disrupting the opponent’s. It’s hard to have an advantage against a normal Jeskai deck because the archetype is so good at switching gears and coming at you from a different angle—this deck largely gives up that capability, resulting in more clearly defined weaknesses.
The deck can spend a fair amount of time spinning its wheels, cycling through Insights and Cruises and not affecting the board. With a Seeker or Mentor in play, it can afford to do that, since simply triggering prowess meaningfully impacts the game, but if your opponent can keep you off of a creature, the excessive durdling can be problematic.
Looking to play a long game without a particularly powerful top end is also a glaring weakness. The plan to outdraw the opponent and win on attrition doesn’t work if your interactive spells don’t trade with your opponent’s cards, which is all too often the case. Esper Dragons in particular exploits this—Jeskai Prowess has far too many dead cards, and is hard-pressed to interact with Dragons and Ugin. Even a GW Megamorph deck that is properly prepared for your creatures will beat you going long since you can’t trade well with their resilient threats.
I find it hard to believe that I’m advocating a Jeskai deck without Mantis Rider, but here we are. Against decks that are not great at killing creatures (such as GW), Monastery Mentor reigns supreme. And against decks that are, or where you can effectively trade 1-for-1, Treasure Cruise is where you want to be. And let’s be real, drawing three cards for 1 mana is ALWAYS where you want to be.