8 speed is not obsolete. Neither is 7 or 6 speeds. Many mini velos and folding bikes, even Dahon come stock with 6 speed.

There are still plenty of 8 speed parts available in taobao even all the way to 2 or 3 speeds.

For Shimano components, you could look for these, from low to high: Altus, Acera, Alivio, Deore, Deore XT.

For me i find Altus sufficiently precise and i don't feel the need to go higher.