Nah, GOG still has their DRM-free claim to fame, as well as lots of games the other two don't have. And many people are strongly anti-EGS. It'll be fine. I'm hitting the GOG summer sale hard this year.
I understand that's what *you* think, and I'm with you. But GOG has done really well in the past by preempting Steam and being the first main sale. That's gone -- they're just between sales now. It's used gimmicks to attract people. That's gone -- Epic has the ultimate gimmick of a free game per week, plus $10 off per order. GOG can't beat that. So that's gone too.
Don't be surprised if GOG's income takes a massive hit this year.