what motivates you?

At this point I think I've actually put more hours into my SSF SP grailing than I have on Bnet. I played pretty hard at d2r launch and played the first ladder for a while but never got to end game. After the S1 economy tanked rather fast (imo.) I decided to try some SP. The SSF in SP is very rewarding and have found many HRs and built a few end game characters and am at like 95% of my holy grail.

Im looking forward to the change up in s2 ladder with sunder charms and I also plan on playing HC this season. I think the economy in HC should be healthier longer so thats my plan for now.

If i get bored of playing d2 i just take some time off. There have been several week or two long breaks in there.

Build diversity and playing chances with RNGesus is what motivates me. I have three mains that I rotate between to grind (90 bowzon, 87 revivomancer, 80 WW/Zerk Barb), and between the three I have fun trying to find nice loot or rune hunting. I also plan on making a couple off-meta builds just for shits and giggles to show that one doesn't need to follow rigid 'Cookie Cutter' builds to be good at the game. The challenge and when you overcome it is immensely fun.

I also like to farm different areas with each of my mains, because for some of them some places and mobs/bosses are better suited for them than others. The WW Barb does fantastic in narrow, tight areas like Maggot Lair, Ancient Tunnels, etc. The Bowzon does amazing in open areas like Act 1 maps, Cows, and Act 5 siege maps. Necro is awesome at bosses, doesn't even need to lift a finger to farm Baal or Diablo. Find what works for you, w/e makes D2R fun and enjoyable, and go for it.

As you mentioned, solo lvl up low-level char is sorta dreadful.

Baal run + tomb raid with others can help refrain that a bit. Aber, you cannot always find teammates to accompany with you when needful.

So I would rather suggest Blizzard to consider open up a new mode which called (public lvling rooms), players can be automatically assigned to 6+ ppl rooms, TZ can be rotated faster, loots will be automatically rolled (or restrict item drop to differentiate with MF purposes), and even monsters can be refreshed. That would be a far better experience for everyone.

But welp on the flip side, I can image if they do so, then probably everyone could end up with 10+ endgame char in about one month and say bye to diablo