Ah mate, have you ever considered going alone? I know plenty of people - some of them very sociable- who regularly take themselves on holiday. In my personal experience it’s much easier to meet people abroad too, even if you’re not usually confident approaching new people (I know I’m not) -somehow those anxieties just don’t have the same grasp on you once you get on a plane. Also if you’re someone ok with roughing it, staying at a hostel is such an easy way to meet cool people. Lots of people in groups are just as keen to socialise - maybe they’ve been travelling with the same people for 6 months and desperately need a new dynamic for a few days.
If none of that appeals you could also try a tour group package? In the Internet age there are probably tour groups for just about every sort of person and every sort or trip. It’s worth shopping around for the ideal tour if you prefer your travels more structured. There are also trips especially for solo travelers, but if you don’t like that idea, it’s perfectly likely there will be people on their own in other sorts of groups too.
So yeah don’t let not having someone to go with stop you. It seems scary before you go, but it’s so much more exciting and liberating than you might think. Plus having a friend there has as plenty of downsides to it! Sorry for such a ramble but i really wanted to share the pleasure of solo travel.... good luck