The level restrictions aren't that much different from Demon's Souls, since the formula is Host Soul Level +/- (Host Soul Level *0,1) + 10. At higher Soul Levels you we're pretty restricted with what people you could play against, that's why Soul Sucking became a very common thing to do, with a lot of over 200 SL players letting themselves being Soul Sucked to starting levels.
Quite frankly, the entire summoning system is almost stricly similar to Demon's Souls, except for the multiple servers/lobbies, which make sense since Demon's Souls had separate servers for each version and Dark Souls is supposed to add players from every part of the world into the various servers. As for the chance of you playing on a lobby with no people, that could happen, but as time goes along and more people buy the game and play online, that becomes a lower and lower possibility. Then again, as you go up in levels the chance that you encounter someone close to your levels also decreases, just like in Demon's Souls.
Don't know why the online system in Dark Souls is getting bitched at. It seems as if people didn't play Demon's Souls or had forgotten how it was.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
