Why do modern actors and directors love classics?

I suspect that you are simply being provocative with your unbelievable and uninformed drivel but I'll give you the benefit of the doubt and assume that you're actually being serious.
You are clearly not and never have been involved in professional theatre and I suspect that your involvement with community theatre has been personally disappointing and unsatisfying, and not for the reasons you give.
I am a former professional actor and have been involved in community theatre as an actor for more than thirty years. Certainly, many community groups choose to do the "classics" and other tried and true works in preference to new works and sometimes they are done badly - but this is more a reflection on the production standards of the particular theatre than on the work itself. I'm sure that such groups would perform new works equally badly.
So-called classics can present formidable challenges to both actors and directors and, because their appeal is perennial, they are good box office which any responsible and well-run theatre must always have an eye to. Having said that, it is my experience that a number of community theatres do not shy away from presenting new and contemporary works but these need to be done sparingly and with sensitivity so as not to alienate their traditional audience base. Afterall, theatre, even that purporting to have a higher moral or social purpose, should be, above all, entertaining. There is no point in putting on plays where the audiences stay away in droves - I have been involved in such productions and I can tell you that, from an actor's point of view, there is nothing more demoralising.
Finally, unless your attitude changes, I believe that community and professional theatre would benefit enormously if you just stayed at home.