The verse says, "basukkot teshvu shivat yamim, kol haezrach beyisrael yeshu basukot". It is a little surprising that the word "sukkot" as well as the verbs are all in the plural, especially in the second half of the verse, where a single "ezrach" is discussed. (Clearly there is no mitzvah for each individual to sit in multiple sukkot.)
Perhaps the verse is hinting that there is a communal aspect to being in the sukkah. Since, ideally, everyone makes aliyah leregel and celebrates Sukkot in Jerusalem, thus Jerusalem should be absolutely crammed with sukkot. And since people are forced to leave their sukkot every once in a while (to go to the bathroom, clean dishes, etc., just to a mention a few required exits from the sukkah), they are guaranteed to see everyone else's sukkot as well as some of the people living in them. Thus, living in the sukkah is an experience you share with the whole Jewish people. This is in contrast to the rest of the year when you are likely to regularly see only your next-door neighbors, if you have any, as well as whoever lives in the nearby town.
This communal experience on Sukkot is similar to the communal experience on Pesach, when everyone after finishing their Seder in Jerusalem would go up to the roof and sing Hallel along with the people on every other roof. The thematic meaning of each communal experience is clear. On Pesach, we commemorate that the entire people left slavery and became God's servants together. On Sukkot, we commemorate that not just individuals but the entire Jewish people are under God's protection.