All the Biblical festivals are there except for yom tov sheni shel galuyot, the second days observed in the Diaspora but not in Israel (except for the second day of Rosh HaShanah, which is observed everywhere).
How the second day came into being has to do with the ancient procedure whereby Rosh Chodesh was declared after eye witnesses testified that they had seen the new moon. Without such testimony it was not certain whether a given month would be 29 or 30 days.
But it took time for the news that it was Rosh Chodesh to reach outlying communities. Hence Diaspora centres added an extra day to Pesach, Shavu’ot and Sukkot in order to ensure that one at least of the two days was the correct date as observed in Eretz Yisrael.
Eventually the calendar was fixed by mathematical calculations, but the second day yom tov, having become firmly entrenched, was retained and the rabbis insisted on its sanctity being upheld.
Some enjoy the second day. Others grumble about it. But there is a positive way to handle it two in fact.
One: if one day is really enough for you, why not consider living in Israel?
Two: give each of the two days a different feeling and flavour. Choose a different shule for the second day if you can; select different menus for the festival meals; invite different guests; go for a different yom tov stroll; prepare different divrei Torah; sing different songs at the table.
In short, let each day make its own distinctive contribution to your Jewish experience.