Ben, as a fairly low-hours PPL without any IMC training (beyond the minimum), I avoid flying in hazy conditions - over land or sea - for the lack of horizon.
I have flown at about 4,000' with an instructor in real clag - no horizon at all, virtual white-out looking straight ahead. It was only possible to remain straight & level on instruments, and without IMC training and experience I would have been struggling to remain straight & level, let alone navigate and communicate!
With the FI looking after the Nav & Comms - and helping to monitor my height, speed and bank, it was just possible for me to fly safely.
Yes, I am sure that with more training and experience I will be able to fly safely single pilot IMC, but I heartily agree with those who say that VFR-only pilots - and those not current in IMC - should avoid these conditions.
It's just that so much of your capacity is taken up with unfamiliar instrument flying that any little fly in the ointment can create an overload, leading to loss of control.
SD