mitzvah - Is serving Hashem in order to receive reward in Olam Habah ideal?

משנה אבות פרק א משנה ג

אַל תִּהְיוּ כַעֲבָדִים הַמְשַׁמְּשִׁין אֶת הָרַב עַל מְנָת לְקַבֵּל פְּרָס, אֶלָּא הֱווּ כַעֲבָדִים הַמְשַׁמְּשִׁין אֶת הָרַב שֶׁלֹּא עַל מְנָת לְקַבֵּל פְּרָס, וִיהִי מוֹרָא שָׁמַיִם עֲלֵיכֶם:

Mishna Avos 1:3

Do not be as servants who are serving the master in order to receive a reward, rather be as servants who are serving the master not in order to receive a reward; and may the fear of Heaven be upon you

גמרא מסכת עבודה זרה דף יט עמוד א

במצותיו חפץ מאד אר"א במצותיו ולא בשכר מצותיו והיינו דתנן הוא היה אומר אל תהיו כעבדים המשמשין את הרב על מנת לקבל פרס אלא היו כעבדים המשמשין את הרב שלא על מנת לקבל פרס

Gemara Avoda Zara 10a

“He delights greatly in His mitzvot.” Rabbi Elazar says: The person delights in His mitzvot themselves and not in the reward for performing His mitzvot. And this is the same as we learned in a mishna (Avot 1:3): Antigonus of Sokho would say: Do not be like the servants who serve the master on the condition of receiving a reward; rather, be like the servants who serve the master not on the condition that they receive a reward.

ספרי, עקב מח יב:

לאהבה את ה' אלוקיכם, שמא תאמר הריני אלמד תורה בשביל שאקרא חכם, בשביל שאלמד בישיבה, בשביל שאאריך ימים לעולם הבא, תלמוד לומר לאהבה את ה' אלוקיכם, למוד מכל מקום, וסוף הכבוד לבוא".

Sifrei Ekev 48:12

"to love the L-rd your G-d": Lest you say: I will learn in order to sit in sessions; so that I merit eternal life in the world to come; it is, therefore, written "to love the L-rd your G-d" — Learn in any event; honor will come as a matter of course.

רמבם הלכות תשובה פרק י הלכה א

אַל יֹאמַר אָדָם הֲרֵינִי עוֹשֶׂה מִצְוֹת הַתּוֹרָה וְעוֹסֵק בְּחָכְמָתָהּ כְּדֵי שֶׁאֲקַבֵּל כָּל הַבְּרָכוֹת הַכְּתוּבוֹת בָּהּ אוֹ כְּדֵי שֶׁאֶזְכֶּה לְחַיֵּי הָעוֹלָם הַבָּא, :

Rambam Hilchos Teshuvah 10:1

Let no man say: "Behold, I perform the precepts of the Torah, and engage myself in its wisdom so that I will receive all the blessings described therein, or so that I will merit the life in the World to Come;

Question: How can we reconcile this with:

מסילת ישרים פרק א ------ Meslat Yesharim (path of the just) ch.1

יסוד החסידות ושרש העבודה התמימה הוא שיתברר ויתאמת אצל האדם מה חובתו בעולמו ולמה צריך שישים מבטו ומגמתו בכל אשר הוא עמל כל ימי חייו.

The foundation of piety and the root of perfect service [of G-d] is for a man to clarify and come to realize as truth what is his obligation in his world and to what he needs to direct his gaze and his aspiration in all that he toils all the days of his life... והנה מה שהורונו חכמינו זכרונם לברכה הוא, שהאדם לא נברא אלא להתענג על ה' ולהנות מזיו שכינתו ...ומקום העידון הזה באמת הוא העולם הבא, כי הוא הנברא בהכנה המצטרכת לדבר הזה.

...that man was created solely to delight in G-d and to derive pleasure in the radiance of the Shechina (divine presence). ... The place of this pleasure is, in truth, in Olam Haba (the World to Come).

This seems to be saying that"perfect service of Hashem" and the "gaze and aspiration in all that one toils all the days of his life" is solely for the purpose of reaching Olam Haba.

Is this not what the Mishna, The Gemara, The Sifrie, and the Rambam call serving the master in order to receive reward in Olam Habah?

IMHO we cannot answer this by saying:

since the Mesilat Yesharim is written for gradual improvement, His statement about thinking about the World to Come is only the motivation for someone at a low level, whereas someone who is at the level of piety (חסידות) should serve only for God's honor with no thought of reward, similar to the different motivations he gives for different groups of people in chapter 4, which are focused on reward and punishment at worst, and self-improvement at best. Serving God for the sake of reward leads to serving him for its own sake, but such a person is still "far from perfection" (chapter 16), and that at the beginning of the book, the reader isn't expected to be at such a level

because the MY writes clearly in his opening statement, that he is teaching us במה צריך שישים מבטו ומגמתי בכל מה שהו עמל כל ימי חייות - to what he needs to direct his gaze and his aspiration in all that he toils all the days of his life" so this is obviously not just a beginners's entry level exercise, but rather the ultimate end toward which one toils and aspires all his life.