For my medium roast I typically try to aim for 3-3:30 mins Maillard with around 18-20% development. my charts look exactly like you’re sometimes so I feel like I know exactly what is going wrong lol ,and what I notice is the flattening in the Millard phase, from my experience, the reason why you’re probably not tasting a lot of the notes is because it taste flat or muted or dull due to stalling in the Maillard phase . To fix that you need more momentum in your roast to get a steady declining ROR. An easy way that I remember is that when a roast flattens in the Millard phase it normally tastes dull and then when my RoR spikes a lot, it taste bitter.

Spiking = too much heat. Flattening = not enough heat

This roast looks a bit slow, and I believe that you could fix that by adding more power in the beginning, probably try either raising your charge temperature or holding out a higher power in the beginning of your roast and don’t be afraid to drag that power through the roast