Those who have read Maulana Maududi’s book 'Khilafat & Malookiat' will know that Umayyad Caliphs were progeny of those of the Banu Umayya who remained strongly anti Islam until the conquest of Mecca. Undoubtedly these were forgiven by the holy Prophet (PBUH) but nevertheless there has to be a difference between those who converted to Islam and suffered hardships and those who did not.
Marwan in particular, who became Caliph soon after the death of Yazid, had doubtful Islamic credentials (Kindly refer to the Khilafat & Malookiat by Mualana Maududi pages 110 & 111 available at
https://www.scribd.com/doc/14008410/Khilafat-o-Malookeyat-Syed-Abul-Ala-Maududi-Urdu ).
The above prelude is only meant to show the reasons why Khilafat changed into Malookiat (hereditary kingship). In essence Umayyad Khalifas as well as Abbasids; despite the fact that they called themselves Allah’s Deputy on earth; were in all but name, Kings not Khalifas. Only exception being Hazrat Umar bin Abdul Aziz, who despite inheriting the Caliphate was an exemplary ruler.
However that aside; Umayyad 90 odd years rule saw unprecedented expansion of the Islamic State. In fact borders of the Islamic State reached their maximum extent during Hisham bin Abdul Mailk. Damascus under the Umayyad was a centre of culture & Umayyad Caliphs have left some splendid buildings such as Dome of the Rock built by Abdul Malik & the Umayyad mosque in Damascus built by his son Walid.
In my view Islamic era had two Golden Ages. Abbasids state under Haroon ur Rashid & Mamun ur Rashid and Spanish Umayyad Caliphate under Abdur Rahman III.
Despite having hundreds of mosques, Spain or Al Andalus (in Muslim chronicles) was largely a secular State. There was complete freedom in the practice of religion. Umayyad rule in Spain had a stratified society. Top positions was held by the Arabs, followed by the newly converted Berbers. Then came the Jews and followed by the Christians. Both the Jews & the Christians had to pay ‘Jizia’ or poll tax.
I have got a book ‘Story of the Jews’ written by Simon Schama. Apparently from the reign of Abdur Rahman III (912 AD) to about 1030 can be considered as Golden Age of the Jews when the Jews held high posts in the Islamic State.
Therefore; irrespective of the fact the Umayyad period, particularly in Spain, would probably be considered abhorrent by the Wahhabis & Da’esh followers; was good for the Muslims. Umayyad rulers in general were great builders. Areas under their rule were economically as well as culturally prosperous & centres of learning. Great Muslim scientist Jabir bin Hayyan (721 to 815 AD) was a product of the Umayyad period.