Mindfulness is very important, but it is part of the path, not the goal. It is the seventh of the eight factors of the Noble Eightfold Path, and the path can be grouped into three trainings. The wisdom training, the morality training, and the concentration training. Mindfulness falls under the training of concentration.
In MN 29, the longer heartwood simile discourse, the Buddha talks about the different reasons for practicing and compares them with different parts of a tree, and he warns against thinking that the parts of the path (including morality, meditation, and wisdom) as being the goal. It says:
"Just as if a man in need of heartwood, seeking heartwood, wandering
in search of heartwood — passing over the heartwood of a great
standing tree possessed of heartwood — cutting away the sapwood, were
to go off carrying it, thinking, 'heartwood.' A man with good
eyesight, seeing him, would say, 'Ah, how this good man didn't know
heartwood, didn't know sapwood, didn't know inner bark, didn't know
outer bark, didn't know twigs & leaves! That's why he, in need of
heartwood, seeking heartwood, wandering in search of heartwood —
passing over the heartwood of a great standing tree possessed of
heartwood — cutting away the sapwood, went off carrying it, thinking,
"heartwood." Whatever heartwood-business he had with heartwood, his
purpose won't be served.'
"In the same way, monks, there is the case where a certain son of good
family, out of conviction, goes forth from the home life into
homelessness, [thinking,] '...Perhaps the end of this entire mass of
stress might be discerned!' Having thus gone forth, he encounters
gain, offerings, & fame. He is not gratified with that gain,
offerings, & fame, his resolve not fulfilled. He is not intoxicated
with that gain, offerings, & fame, not heedless about it, and does not
fall into heedlessness. Being heedful, he achieves consummation in
virtue. He is gratified with that consummation in virtue, but his
resolve is not fulfilled. Because of that consummation in virtue he
does not exalt himself or disparage others. He is not intoxicated with
that consummation in virtue, not heedless about it, and does not fall
into heedlessness. Being heedful, he achieves consummation in
concentration. He is gratified with that consummation in
concentration, but his resolve is not fulfilled. He is not intoxicated
with that consummation in concentration, not heedless about it, and
does not fall into heedlessness. Being heedful, he achieves knowledge
& vision. He is gratified with that knowledge & vision, his resolve
fulfilled. Because of that knowledge & vision he exalts himself and
disparages others: 'I dwell knowing & seeing, but these other monks
dwell not knowing & not seeing.' He is intoxicated with that knowledge
& vision, heedless about it, and falls into heedlessness. Being
heedless, he dwells in suffering & stress. This, monks, is called a
monk who grasps the sapwood of the holy life, and with that he falls
short.
"Furthermore, there is the case where a certain son of good family,
out of conviction, goes forth from the home life into homelessness,
[thinking,] 'I am beset by birth, by aging-&-death, by sorrows,
lamentations, pains, distresses, & despairs, beset by stress, overcome
with stress. Perhaps the end of this entire mass of stress might be
discerned!' Having thus gone forth, he encounters gain, offerings, &
fame. He is not gratified with that gain, offerings, & fame, his
resolve not fulfilled. He is not intoxicated with that gain,
offerings, & fame, not heedless about it, and does not fall into
heedlessness. Being heedful, he achieves consummation in virtue. He is
gratified with that consummation in virtue, but his resolve is not
fulfilled. Because of that consummation in virtue he does not exalt
himself or disparage others. He is not intoxicated with that
consummation in virtue, not heedless about it, and does not fall into
heedlessness. Being heedful, he achieves consummation in
concentration. He is gratified with that consummation in
concentration, but his resolve is not fulfilled. He is not intoxicated
with that consummation in concentration, not heedless about it, and
does not fall into heedlessness. Being heedful, he achieves knowledge
& vision. He is gratified with that knowledge & vision, but his
resolve is not fulfilled. Because of that knowledge & vision he does
not exalt himself or disparage others. He is not intoxicated with that
knowledge & vision, not heedless about it, and does not fall into
heedlessness. Being heedful, he achieves a non-occasional liberation.
And it is impossible, monks, there is no opportunity, for that monk to
fall from that non-occasional release. [1]
"Just as if a man in need of heartwood, seeking heartwood, wandering
in search of heartwood, cutting away just the heartwood of a great
standing tree possessed of heartwood, were to go off carrying it,
knowing, 'heartwood.' A man with good eyesight, seeing him, would say,
'Ah, how this good man did know heartwood, did know sapwood, did know
inner bark, did know outer bark, did know twigs & leaves! That's why
he, in need of heartwood, seeking heartwood, wandering in search of
heartwood, cutting away just the heartwood of a great standing tree
possessed of heartwood, were to go off carrying it, knowing,
"heartwood." Whatever heartwood-business he had with heartwood, his
purpose will be served.'
http://www.accesstoinsight.org/tipitaka/mn/mn.029.than.html
This Sutta makes it clear that it is incorrect to identify a part of the path such as mindfulness as somehow being identical with the goal. Mindfulness is a tool, not the result.
