Number of messages does sound rather uninvasive, but as far as my brushes with Data Protection go, anything that analyses anything in your stored data (message logs, servers you're on, friends etc.) they are required to get your consent. "Personalise discord experience" is fancy wording for "we analyse your data for stuff you want that is convenient to you". I think you want something that's very surface level but is legally in a different category, which makes it look like they're blowing it out of proportion. Which is fair! That does look weird and out of pocket!
I'm a teacher for IT, and data protection is one of the topics that is important but hard to connect to everyday live. It's convoluted and expressed in language that is meant to be exact, not intuitive. I think its better for Discord to ask you if you allow them to do the action you want them to do, if that action requires more insight into the patterns of your personalized data as set previously. Thats a good thing! Autonomy!
How much else besides your request are you allowing by clicking on agree? Don't know. Does Discord have a monetary incentive to analyse your personal data? Don't know. What are the laws that apply to you specifically? Don't know. But for all I know you can click allow, do what you want, and revoke the agreement afterwards. You open the door, show them what to analyse, then tell them to leave and they have to.
Some of the fundamental data rights you have are to make them delete the data they have on you, change your mind on permissions you give and limit how much they are allowed to process your data.
Data is stored, patterns are inferred and information is what we subjectively make of those patterns.
