You don’t need to worship all of them (you can try, but I don’t think you can have any significantly meaningful relationship through that), however, you can honour them all.
Tess Dawson makes a good point about it in her post on piety. Piety most certainly involves respect and honour towards others’ gods as well as our own. That’s one of the beauties of polytheism, after all. Worship foreign gods? No problem, invite them over for supper!
Most people will tell you to start with only a few gods, and I don’t necessarily disagree with that advice (for most people, I would say the same), but honouring them all at once doesn’t seem such a bad idea, either. Our ancestors, in their childhood, were probably introduced to their gods as a whole before getting to know each of them. Maybe–just maybe–it could work for you, too.
I’m not sure if there’s an historical precursor to this, whether within the ancient Mediterranean world or beyond, but I make it a point to honour the All-Gods (i.e. the Divine Assembly, the Divine Kindred, etc) at least once a month, usually on the ninth or on the full moon.
I name the ones that are commonly given cultus in my family, then followed by “and all the gods and goddesses my ancestors worshipped; the gods and goddesses of the Aegean and the Balkans, the seven hills of Rome, the Two Lands about the Nile, the white mountains of old Phoenicia, and all of Asia east of Hindustan”. Yeah, I’m wordy like that. Feel free to phrase your pantheonic hymns however you like.