Scribus is not, I repeat not, a Office-suite with as much packed in it as ever is possible. Scribus is a Desktop-Publishing program, intended to produce documents who will be printed. This mens à priori, their documents are not dynamic. Once something is printed, nothing can change the print.
Scribus is also based on real type-setting realities. HTML has nothing to do with type-setting, it is a dynamic language. That the tags H1 to n are more or less similar in their outcome is pure luck. Tables here are also not dynamic, there is no calculating engine inbuilt. You need to type in each figure. Or make an illustration of a Calc or Writer-Table and import this into a picture frame. This is two tousand times faster than any fidgeting with including tables.
As an ex type-setter, I love Scribus, it is really like it was in the sixties and seventies when I worked with lead making books, pamphlets, magazines and newspapers. Only now much healthier (no lead letters) and I can sit at work.