Besides works versus grace and indulgences, what were the external practices of the Catholics that offended so many reformers? My question is not focused on the doctrinal issue, but on the external practices which were contributing to the division. For example, I know there were many 'image breakers' similar to traditional Jewish views, who even took a swing at Luther for having pictures in his Bible, whereas Luther was a little more middle of the road with regards to images and statues. So long as they were not used in anyway that might suggest invocation to Mary, or the Saints, which turned them into proper idols, he did not see a problem.

The question therefore, is NOT should this thing, or that thing, be offensive, but 'historically', what was offensive?
Book IV of Calvin's Institutes of the Christian Religion deals with many objections to the practices of the Catholic Chruch, frequently with rather harsh language.


The claim that the Roman church is the only church (Chap II.2)
The communion as practiced by Catholics is idolatry: "The foulest sacrilege has been introduced in the place of the Lord's Supper."
Reliance on Church teaching instead of the Bible (Chap II.4): "Paul reminds us that the church was founded not upon men's judgements, not upon priesthoods, but upon the teaching of apostles and prophets [Eph 2:20]."
Elders should be elected (Chap II.15). Reference is made to Acts 14:23, which seems to have a disputed translation, but also to the practices of the early churches.
Bishops should not have ostentation or pomp (Chap IV.7)
Examinations  of church leaders  was not done, or if done was not based on ability to preach. (Chap V.1)
The Church did not reject interference by princes (Chap V.3)
Church titles are conferred without regard to need (Chap V.7)


It goes on like that for hundreds of more pages.