Elizabeth was seen to be weak merely because she was a woman. In Tudor times, a man was seen as being:

Physically strong so they could control ambitious nobles from different factions and lead the army in battle.
Decisive.
Able to be a religious leader.

Before Mary I, the last time England had had a female monarch was Matilda in the 1100s and this had caused Civil War. In the 1500s people also looked back on the chaos and bloodshed of the Wars of the Roses during the previous century in which rival families fought for control of the monarchy. Finally, after breaking with Rome, Henry VIII had made himself Head of the Church. It was unthinkable at that time for a woman to take this role.

A Scottish Protestant, John Knox, was fierce critic of female rulers and wrote a book The First Blast of the Monstrous Trumpet.

Consequently, Elizabeth's gender was an issue that added to her problems when she came to the throne. Everything in history is linked and this issue was intertwined with the questions of religion and marriage. However, there were successful female rulers of other countries at the time, for example Mary of Guise in Scotland. Elizabeth over time used her gender to her advantage, developing the image of the Virgin Queen, married to her realm.

GCSE Elizabethan England 1568-1603 AQA

Elizabeth's Gender