[SNosTrAnDbLe]

By definition, microservices are independent of stack. Every service in theory can have its own stack. My recommendation would be to stick with microservices but start migrating each service to modern stack. With regards to the stack, you can look at Django if you want to move to a python based ecosystem, Spring boot for java and node if you want to look at server side js backed by a classic RDBMS like MySql or Postgres