You're just wrong.
Blackshark issue was caused by developers because they implemented a DRM on top of steam DRM. This is not related to steam at all. Good riddance, such developers shouldn't be allowed on steam.
Steam is more convenient. All the addons work.
Steam is not a DRM itself, it acts as DRM only if developers want that. There are plenty of DRM free games on steam. I'm not sure but i think X-plane 11 has no steam DRM.
If you worried about cpu and ram usage with steam open, then you need a new computer. It's the most popular platform for games, if it would interfere with game's performance it wouldn't be so popular.
Laminar put x-plane on sale few times a year on steam. Like it is now 34% off.
Steam doesn't manage it, laminar manages it through steam. It's for laminar to decide what DRM to use, when and how often to update the game, what features to add etc.