Hi,
I see problems.
Mainly because the power input, to the relay output .. these are the most noisy signals mayby carrying high currents, switched currents.
The longer the traces the better (= worse in the meaning of EMI) the antenna to send out the noise. Thus keep it short.
I´d isolate them from the other more sensitive signals as good as possible. Otherwise they may cause the ESP to become unstable / reset.
My approach looks something like this.
The red arrow just shows the short, direct path of the most noisy power signals.
The green line across the relays shows where I´d put a split in the GND plane. A wide split, maybe 5mm or more.
The next rather noisy switched signals are the relay coil signals. They get their own path from right (power supply ) to the left (relay coils).
The next green line shows again where a split in the GND plane could be.
Mind that each "C" shows where I´d put a capacitor for power supply decoupling.
Then you see a very short path from power supply connector to the power supply.
(The power supply can be seen as a star point to distribue power in individual dirty and clean paths.)
From the power supply you now could easily provide the "dirty" power to the relay coils and the clean power in direction to the ESP.
Mind the antenna gap for the ESP!!!!
****
The rest of your circuit is rather uncritical and may be placed in a way that the GND plane is most solid.
Bottom side should be GND. GND, GND. Best when there are no other traces. And when there are traces they should be short not to cut the plane into pieces.
With my approach you will find it way more easy to get a solid GND plane.
***
Maybe you are not aware. But in your blue layer there is a wide area in the center of the PCB. Looks nice, solid, but indeed it´s useless. There is no via, no connection, no current. It does nothing.
But when you follow the GND on your blue layer:
Power connector --> right to the power section (getting dirty) --> in a narraw path to the most right bottom corner --> then to the right top --> supplying the ESP --> then back to the left to the dirty relay coil section.
For sure it is supported by the GND in the red layer .. but it is way worse than all GND just in one layer and the signals in the other layer.
Maybe you have the time to do a redesign, maybe not. If not then keep these ideas in mind for your next project.
But if you do a redesign: Do the placement first, no routing. Just show us the raw part placement. Then we can discuss the next step while not wasting a lot of your time.
Klaus