I've seen most musicals and generally the new ones aren't as good as the oldies
Are you specifically talking West End musicals? Because there have been some amazing "new" musicals (i.e. within the last decade), both off-West End and on Broadway that maybe haven't reached here yet or didn't make much of a splash over here. Waitress, Dear Evan Hansen, In The Heights, Once, London Road, Spring Awakening, The Addams Family, Groundhog Day, Bright Star, Come From Away, Fun Home... I think the past decade has really seen musicals come into their own and blow the traditional Lloyd Webber / Schönberg & Boublil canon out of the water.
That's not to mention some of the lesser-known late 90s / early 00s musicals like Parade, The Color Purple, The 25th Annual Putnam County Spelling Bee, Urinetown, Floyd Collins, The Light in the Piazza etc etc.
(I probably care too much about musicals.)