Stellaris

Ten years old and still getting major updates, reworks, and new content, most of the important stuff free. Paradox could have moved on to a sequel a long time ago. Instead they keep tearing out systems that don't work and rebuilding them, which is why this is still the best 4X on the market and not a museum piece. On the DLC, since that's what everyone worries about: don't buy it up front. Play the base game. It's a complete game on its own, though after enough hours you'll start feeling the edges where expansions slot in. When you want more, subscribe to the expansion pass for a month, try everything, then buy the ones that changed how you play. It costs about as much as a couple coffees and it's the best "try before you buy" model I've seen in any game. I've played basically the same tech-focused federation empire for hundreds of hours, so Federations is the expansion that actually changed my game. Yours will be different, which is the whole point of subbing first. Big releases have a rough first week or two. If that bothers you, wait, that's what the beta branches are for. If it doesn't, start a fresh save and enjoy the chaos with everyone else. Hundreds of hours in and I'm still finding new stuff. Great game, great studio.