In particular, aggregations need to be defined using the special AggregateFunction data types, which must be paired with the corresponding aggregation functions such as countMerge(). Joins are possible in CH views, but they operate in a specific way (against the insert batch) that you must know about; joins against other tables are generally a bad idea for performance, and you should use dictionaries as much as possible for fast in-memory lookup. Lastly, it's also hard to update MVs because their entire source query has to be modified as a whole. Adding a column requires declaring the whole MV, which introduces the possibility of making mistakes in your migrations.
CH views are really more like triggers, and so they're a little misleadingly named. Very powerful, of course. In short, a lot more "manual" than this other system.
That said, we are /not/ a replacement ever for Clickhouse or any other historical warehouse. In fact, we pair best with one of them. Have data flow through or teed into Feldera to maintain sophisticated standing queries -- maintain historical data in your warhehouse.