I don't think anyone is saying that this is ruining the game.
The discussion is about whether or not you can run missions effectively in a limited timeframe, for players who may not be able to dedicate long play sessions.
The perception that this content would be restricted to players who can dedicate multiple hours of play is a valid concern worthy of discussion.
I personally think that this is untrue, but it's worth discussion, especially considering that there are numerous other ways that the game disincentivises infrequent play, like rep decay, the whole powerplay system, etc.
That phenomenon does stand to threaten the enjoyment of the game for players that are unable to log as many consecutive hours, and that's not a good thing.
I don't think the game is ruined, but I also don't see many concessions being made for "casual" (in terms of how often and for how long they play, not in terms of investment or skill) players, so it is a real and worrying trend.
Some people are saying it ruins the game however, and that's part of what I was addressing, but only a part.
The rest is exactly what you stated, that the game doesn't cater to casuals, because it doesn't. It doesn't cater to anyone, it's a sandbox universe game, missions are a mini-game inside the game world, they are not THE game, just a mini-game. People who don't have any time to devote to doing missions don't have to, they suffer no repercussions for that, they simply don't get the benefits of doing missions, if there are even any benefits for doing missions. Rank in the Federation and Empire is gained by doing missions for specific factions allied to them, and all that rank gets you is access to some ships, ships that aren't even the best possible ships for their price ranges/tonnage/mission profiles. And anyone can get the rank to access those ships by doing a single mission at a time as they have the time to do them, it may take them a longer time frame than someone who's able to devote hours at a time to doing missions for this specific purpose, but the time spent will be the same for both as it takes the same amount of missions regardless of doing them in batches or one at a time.
Power Play, easy enough for a casual player to do it as well, an hour here or there during a week is enough to get to rank 4 and keep it without any issues at all. I spend maybe 2 hours a week doing PP specific things like delivering reports, delivering fortification supplies or fighting in Crime Sweeps, none of which are time sensitive other than needing to be done between the start of the PP week and the end of the PP week. PP isn't a mission driven thing, it's a specific action driven thing, delivering reports, killing enemies, fortifying with supplies, things you can do with an hour's play a few times a week for rank 4 quite easily. Rank 5 is the only rank that requires some effort, and if you are a casual player, well, if you want that 50 million credit salary a week, you should have to do something more than just show up once in a while, don't you agree? Don't ALL of you agree with that?
And again, missions and Power Play are mini-games inside Elite Dangerous, you can do them or not without it having any negative effects on your gaming. Getting credits, earning ranks in Trade/Exploration/Combat can all be done without touching a single mission or ever bothering with PP. You can earn enough to own every single ship in the game and outfit them however want without doing a single mission, although to get access to Faction specific ships you will need to do some missions for those specific Factions, but you can take as long as you like to do that, it's not a 'you must complete X number of Faction missions in X time frame or ELSE!' thing. Do 1 mission for the Faction every few days, or better yet, don't do any missions, just make contributions to the Faction, you know, those 'help repair our station in the name of' that pop up on the BB? Those are the BEST way to get good rep with a Faction, and they take 0 time to do. So if you just HAVE to have a Federal Dropship or Imperial Clipper, start making contributions to the Factions whenever you see them pop up, you'll get there eventually, without having to do any actual missions at all.
If you want to actually have a direct influence on the BGS, you need to devote time to that, sorry, but that's just how it is, and they shouldn't change that to cater to people who can't or won't devote any time to it, as it's not exactly a little thing to change the socio-political landscape on a single planet, much less for an entire star system or systems. People who actually want to do that aren't casual players to begin with, they WILL find the time to devote to the game to do those things, it means something to them for whatever reason.
The OP didn't do missions because of a feeling that they take too long to do. It's been pointed out that that is a misconception, most missions take a few minutes to complete, only a few take longer, and you can easily avoid them while doing lots of other short time missions.
I noticed that people feel like missions are a big part of the game and if they can't do them they are missing out, or that they need to be MORE whatever to make the game better, and I pointed out that the missions are just a mini-game, Elite Dangerous is a real sandbox game, there is no overriding directive to do any specific thing, you can roam about and do whatever you want at any time and progress in the game however you want.
