Serious took over fun. Game is not worth playing anymore.
I think I would disagree with this statement in the strongest possible terms.
I think Oolite is still, and always has been, a fun game to play. All the core elements that made the original Elite so enjoyable are still here in Oolite, and will always be here.
I'm not sure what you mean by "serious". As a simulation of what real space exploration, trading and combat would be like, I don't think even Elite could claim the term "serious". How big are those planets? How far is it to the sun? Just one planet per system? Elite and Oolite were designed to be fun to play, not a "serious" simulation.
Tad more than 6GibB of stuff.
A vanilla installation of Oolite 1.86 has a download size of around 100mb, and on my Windows PC installs to around 170mb. To get up to 6Gb of stuff you must have OXP's installed. And if you're dealing with a game you feel is no longer fun to play, then I would suggest your OXP loadout is unbalanced. The recommended approach to OXP's is always to start with very few, then add them to the game slowly so you can assess whether you think the expansion makes your game more or less fun.
If your issue is with a particular OXP, then the author would probably love to get your feedback. Suggestions on improvements are always welcome.