Re-read that entire Amendment. Notice there is a comma after “assemble” followed by “and”. Do you comprehend what that means?
“...or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.”
While peaceably assembled they may also petition the government for a redress of grievances.
But then understand that the 1st Amendment applies to the States via the 14th Amendment, which says that no person shall be deprived of life, liberty or property without due process of law. Courts have held that the substantive aspect of “due process” has its parameters within the first nine articles of the Bill of Rights; ie, “liberty” with “due process” means the rights guaranteed against the intrusion of the federal government. Those rights are also guaranteed against the states, thanks to the “due process” clause of the 14th. But they’ve also routinely qualified those rights against the state as only applying when a state has no compelling state interest recognized by the courts. If there is a legitimate, compelling state interest, due process is satisfied.
Thus, the freedom to assemble without even asking for a redress of grievance, but only to celebrate a baby’s birthday, is insufficient against the state’s right to prevent the spread of deadly infections. Sorry. You’re strong on grammar but weak on the law.