The sages were sympathetic to those who did not understand Hebrew. They list prayers that may be said in another language: Shema, Grace after Meals and the Amidah. Most rabbis rule that if absolutely necessary, people may recite everything in their own language.
That does not mean that we needn't bother with Hebrew. As Franz Rosenzweig (1886 – 1929), who became observant after attending a traditional Yom Kippur service, wrote, "The uncomprehended Hebrew gives him more than the finest translation… Jewish prayer means praying in Hebrew."
The Mishnah Berurah teaches that it is a "choice mitzvah" to say the Shema in Hebrew because of the difficulty of translating it without losing the layers of meaning and because "it is not found that a child of Israel does not know the first verse of the Shema (62:3)".
Prayer in our vernacular should serve as a safety net, with Hebrew (with comprehension) as the ideal. With all the translations available, that is a reachable goal.