What an online casino actually is
An online casino is rarely one company. The brand you see is the operator: it holds the licence, takes deposits, runs the accounts and pays withdrawals. The games themselves are almost never built by the operator — they are licensed from game studios such as Pragmatic Play, Evolution, NetEnt, Play'n GO or Hacksaw, usually through an aggregator platform that plugs hundreds of titles into the site at once.
That separation matters to you as a player. The same slot with the same RTP can appear on fifty different sites, so the game is not what differentiates them. What differentiates them is the operator layer: licence quality, withdrawal speed, bonus terms, KYC behaviour and support. Judge the operator, not the game list.