The short answer is yes we need a star. If we would like to compete long term in the playoffs, then a star is fine. However, some would argue that the ultimate goal of this rebuild is to contend for a title. Unfortunately, stars don't win finals. Superstars win finals (when surrounded by a high level of talent.)
Kevin Love, and Cousins also would not fit into the historical mold of what a superstar is. A superstar is an MVP caliber talent. (This is what erks me when people refer to melo as a superstar.) This doesn't mean they are MVPs at the time, but the talent to win MVP doesn't simply leave. They are still at that level of talent, even if their stats decline, and they sacrifice more for the team. Most of you will probably chastise me for this stance, but let me give a little historical background.
2015- GS won with Curry (current MVP) and a wonderful supporting cast.
2014- SA won, and while they do exemplify a beautiful team concept, they also have Duncan, a 2x MVP winner (who also plays better than any 38 year old I can remember)
2013, 2012 - Heat won, and Lebron needs no introduction
2011 - Dallas- Another great example of team effort. However, from a talent standpoint, they had Dirk (07 MVP) and Kidd
2010 and 2009 - Kobe (08 MVP) and a huge amount of talent around him
2008 - Our good old days - Celtics won- Garnett (04 MVP), Allen and Pierce (about as good as you can get w/o MVP nod) and a great supporting cast
2007- Spurs - Little Timmy even closer to his prime
2006 - Heat win- Wade (one of the few not on this list with an MVP, but still top 3 player that year), and they had a past his prime Shaq (MVP 2000, still averaged 20 and 9 that season)
2005- Spurs - welcome back guys, wont be the last time they are on the list
2004- Pistons - as many have pointed out, this team was without an MVP type player. This should really drive home how rare it is to win without that level of talent
2003- Spurs - oh god we have to stop meeting like this
2002, 2001, 2000 - Lakers - MVP Shaq, and young athletic Kobe (future MVP)
1999- Spurs - Man did I mention Duncan and the organization is good or what?
1998, 1997, 1996- Bulls - Greatest player of all time and great supporting cast (if you can even call Pippen and Rodman just supporting cast)
1995, 1994 - Rockets- Hakeem (94 MVP, would be more if Jordan didn't exist)
1993, 92, 91 - Bulls- Jordan
1990, 89 - Pistons - great tough nosed all around team, no MVPs (Isaih was better than anyone we have any chance at getting, but we will count this team)
I stopped the list here, but as we head further back into the 80s the Lakers and Celtics really hurt the "no MVP level superstar talent" even more.
Final tally- between 2015-1989 (27 championships) 23/27 times the winner was a team with MVP level of talent on the roster. Not just stars.
This is a very sobering thought when we think about our chances of winning the ship any time soon, because out of the group of Smart, Love, Monroe, Cousins, Harris, none are even close to the level of talent needed to win a ship.
Anyway, lets go Cs.