Yes they can. You need a good learner's dictionary to know if a word is countable, uncountable or both. For example, this entry shows that the word "noun" is countable https://www.collinsdictionary.com/dictionary/english/noun There are no rules on "countability" that relate to the type of suffix. You have to learn words individually and notice patterns over time.

I have an idea of what you mean. Many (if not all) of those endings, came to English through Italian and Latin. Many of them are used for abstract concepts which normally have no singular nor plural. For example "luggage" is uncountable (-- "a lot of luggage to carry on"), but "marriage" can become "marriages" if needed (-- "two marriages at the same time" ). Good study

assignment → assignments dimension → dimensions motion → motions hyphenation → hyphenations beginning → beginnings approval → approvals gallery → galleries balance → balances urgence → urgencies pressure → pressures bondage → perverts ignorance → ... I guess it is customarily used only in singular One great way to understand the nature of a word, is to look up in a good dictionary. We would like anything to have a rule, but luckily our World is much more complex. However, in Science field, they say that you can make a Law only if it explains everything else.