Most of Europe would beg to disagree.
The great advantage of coalition government is that it the partners act as a moderating influence on one another.
Also, you tend not to get 'grand coalitions'. Instead, you get a senior member with enough junior members to create a stable voting bloc. Grand coalitions only happen at times of perceived existential threat or national crisis. The closest thing to to a counterexample I can think of is Austria, but even then, those were to put a cordon sanitaire around far right and far left parties. The very fact that grand coalitions are seen as antidemocratic tends to keep their formation to a minimum.
In reality, countries that have lots of coalitions by virtue of their voting system (such as STV[1]) tend to have perfectly stable governments. It's only in countries whose voting systems tend to give a single party power that have issues with coalitions, because they have no idea how to handle situations like that. Witness the panic in the UK after the 2010 elections - here in Ireland, we were quite entertained by the panic as coalition governments are the norm here.
[1] Ireland, where I'm from, for instance, hasn't had a non-coalition government since the '50s. In that time, we went from being one of the poorest countries in Europe of one of the wealthiest in the world, so obviously our government was able to take some kind of meaningful action in all that time.