It depends on what exactly they feel harmed by.So, does that mean you feel Apple is indeed being "harmful" to app developers and marketers by its restrictions on alternative app stores, payment systems, sideloading, etc.?
For example, iTunes makes it easy for me to terminate an app subscription without having to interact with the app itself (which could be useful if I had previously deleted the app already). If app developers want to get around this so they can earn more by making it harder for users to cancel their subscriptions, then that's a move which really isn't in the best interests of the consumer.
I feel that's one aspect of the conversation that hasn't gotten enough attention - that what's beneficial to developers may not be good for consumers (and to be fair, vice versa). And it's not surprising that companies like Epic and Spotify aren't drawing attention to the less consumer-friendly aspects of their business.