How big of a problem is it having large lists with hundreds of thousands of items and views that grab 'em all out with no filtering what so ever?
The magic number of 5000 items per view circulating all over the internet says that's a big no-no because of how SharePoint are querying the content database.
But we've tried raising the treshold limit at farm level to some really high values noticing... absolutely nothing. It just works.
What will/can happen in a worst case scenario? Some slow performance now and then or a total irreversible disaster?
SharePoint 2016 on prem with approximately 2000 frequent users.