At the luxury end, you might wish to consider Crystal Cruises. The single supplement for non-balcony rooms is only 30%. Loads of solo passengers on Crystal. I have even seen the single supplement waive of specific cruises which are quieter.

Crystal prices are pricey but it is at the luxury end and is all inclusive. I have also see events organised for solo passengers and in the evenings there are Ambasadors Hosts for dancing with solo female passengers. They have now taken on an Ambasador Hostess to test the market.

Crystal offers a choice of fixed time dining or dining by reservation (you can book for a different dinner time every night). If you go for fixed time dining, you will be sat on large table; sometimes only solo passengers, sometimes with other couples or groups which gives a good opportunity to mix and mingle.

If you are concerned, despite being all-inclusive, it is still a very quiet crowd so you will not see drunk passengers slumped on a deck chair in the middle of the day. There is a good selection of well-know spirits, a fixed selection of red and white wines (about six of each); premium coffees/teas, bottles of mineral water (even to take off the ship for excursions). Food is of a very good quality. Evening entertainment is excellent.

You do have to pay for organised shore excursions although free shuttle buses are normally provided if the ship docks some distance from town.