Everything, maybe. As we can more widely blame 13 years of Tory failure.
EU roaming is definitely a direct result of Brexit however. EU roaming charges were only removed because of the EU, so leaving the EU they were obviously going to return.
I'd argue the opposite. Socio-economic effects take a long time to properly realize from low-key but widespread changes. It's only starting to actually have a real effect, basically. And there's so many secondary and tertiary ripple effects, like even more medical professionals trying to leave whenever they can, further depleting the health care system, etc.
Of course, it's not necessary to specifically focus on people voting for Brexit to, we could expand this and say that the Tories were kept in power long enough to ensure they could completely fuck over the UK economy and society. Brexit is just one - albeit big - part of that.
My experience is that EE are pretty decent - pretty decent and well-supported network, and brilliant customer service. Even the £2/day charge to use your package allowance while roaming wasn't brilliant, but wasn't terrible either.
I took both my contracts elsewhere this month after 13 years though because price-wise, they just take the piss. I've got a phone that's almost brand new after an insurance swap, so I only wanted a SIM-only month-to-month contract, and they were easily at least 50% more expensive than the rest, even without the other sneaky shit like throttling, 4G-only provision, and such like on some packages.
Fuck that. They've gotten greedy. Quelle surprise.
Jumped to Lebara once Three started charging for EU roaming. Uswitch have a nice plan with 21GB/month for about £8–9/month. Includes EU roaming. No lock-in or contract. I think it also includes some free minutes to dial EU numbers. Pretty much better in every way.
Basically the same story here, but I moved from Vodafone to Smarty. £15/mo for unlimited data and includes free EU roaming (10GB limit, IIRC). It's weird that Smarty, a budget subsidiary of Three, offers free roaming but Three doesn't.