Funny enough, I went through exactly the same headache a while back. After jumping between a few disappointing sites, I stopped chasing flashy welcome offers and started comparing the basics first. In the middle of that search I found
Casinos online, which pointed me toward checking licenses, real withdrawal speeds, available payment options, mobile compatibility, responsible gaming tools, and whether the casino works with well-known software providers instead of random ones. Since then my choices have been way better, and I haven't had to argue with customer support over every little thing. Takes a bit more time at first, but it definitely saves plenty of frustration later.