In Parshat Emor the holiday of Shavuot is presented as an extension of Pesach.
Sefer HaChinuch, Mitzva 306 explains how the two holidays are linked:
The very lifeblood of Israel is the Torah. Heaven and earth were only created because of the Torah… The principal reason for Israel’s deliverance from Egypt was their acceptance of the Torah on Mount Sinai and their observance if its laws…This was the main motive for their deliverance, this is their purpose in life and this was more important than freedom from serfdom…and it was for this purpose they were taken out of Egypt and were made into a great nation that they were commanded to count the days and weeks from the second day of Pesach until the day on which we were given the Torah. Thus we show our delight in and yearning for the great day as a servant longingly counts the days until his liberation. The counting is an expression of eagerness to reach that day…
Nechama Leibowitz points out that Rabbi Yehoshua ben Levi (Shir HaShirim Raba 7:2) gave Shavuot the name Atzeret (concluduing festival of Pesach) to mark it as the sequel and culmination of the Feast of Deliverance from Egypt in the spirit of God’s promise made to Moshe at the burning bush (Shmot 3:12) “When you have brought the people out of Egypt, you shall serve them on the mountain.”
We see from here that the Exodus from Egypt was not complete until we received the Torah. The holiday of Pesach is only fully observed after we celebrate the holiday of Shavuot.
Unlike Pesach which is a difficult holiday to prepare for and observe due to the food restrictions of not eating Chametz, Shavuot is relatively easy. Although there is a custom to eat dairy on Shavuot there really are no food restrictions and many eat meat as well since they believe that a holiday is only fully celebrated by eating meat.
Why then is Pesach celebrated so much more than Shavuot with many Jews outside of Israel not even knowing about the existence of the holiday?
Shavuot doesn’t have a set ritual like the Pesach Seder. In Israel, many Israelis, despite their affiliation or denomination attend all night learning programs on the eve of Shavuot where the Torah is made accessible to the Jewish community at large. Outside of Israel, these all night learning programs are usually set up in synagogues and those who are not affiliated may not know about them or may be hesitant to attend. The time has come for Jewish community centers throughout the world to bring the holiday of Shavuot to the entire Jewish community and to provide Torah study classes that Jews of all backgrounds would feel comfortable attending emphasizing the fact that the Exodus of Egypt was only complete once the Jewish people received the Torah.