There is no problem buying the parts separately needed to build such model. Of course, some exotic parts were discontinued. Lego provides instruction as pdf on their website.
Edit: the other brick manufacturers have problems replicating brick quality with injection molding machines. I assembled thousands Lego parts with my son and their fit was exactly the same - perfect. The Chinese kits have one in hundred parts that doesn’t fit well. However it was one in ten some years ago, Chinese learn fast.
I doubt one can 3D print anything as Lego replacement.
Competitor brick quality is on par or better than Lego at least for some. You need to do a little research on which competitors use which brick producer, but for example the bricks I’ve had in the Mould King sets were absolutely indistinguishable from Lego bricks in quality.
Building Mould King right now. The difference is almost gone. Cada is worse than Mould King. Anyway with 5x price difference I can live with a bit lower quality. Lego pricing is just sick. Even used sets from not that distant past.
Edit: the other brick manufacturers have problems replicating brick quality with injection molding machines. I assembled thousands Lego parts with my son and their fit was exactly the same - perfect. The Chinese kits have one in hundred parts that doesn’t fit well. However it was one in ten some years ago, Chinese learn fast.
I doubt one can 3D print anything as Lego replacement.