I have used a number of services to Gatwick and it varies.
Thameslink to London Bridge: 30 minutes+
Thameslink to Farringdon: 1 hour.
Thameslink to City Thameslink: 1 hour.
Thameslink to St Pancras: 65 minutes.
Southern to London Bridge: 70 minutes.
Gatwick Express: 30 minutes.
So aside from the Gatwick express, most services to Central London are in excess of 50 minutes, which is a longer journey than the Greater Anglia operated Stansted Express.
I don't think the Stansted Express is pathetic, it operates every 15 minutes and only takes 30-40 minutes. The service has wifi and is operated by class 379 trains which are under 7 years old, aside from the Thameslink class 700, the other operators use older trains. If you use Southern, you run the risk of having your service cancelled with their strikes, which btw are ongoing at the moment.
So, I think your issue is outright snobbery.