There are all sorts of ways to critically appreciate this poem.
You can start by looking at where the poem first appears and what form of poem it is. With just a little digging, I found that "Reluctance" is a lyric poem from Robert Frost's earliest collection, A Boy's Will (1913). There's more to say about what makes this poem a lyric poem, of course, and that explanation would focus on the speaker in the poem and on the poem's subject.
You can continue to look at the form of the poem, reflecting on how it's built. It has 24 lines, broken into 4 stanzas of 6 lines each. You can look at meter, maybe noting that the final line is shorter than all of the other lines in each stanza. The first five lines have three beats each (trimeter) whereas the final line has only two (dimeter). Here's the meter of the final two lines of the first stanza, using capital letters instead of the usual tick mark, to show the stressed syllables or beats:
I have COME by the HIGHway HOME,
And LO, it is ENded.
You can also look at the rhyme. Noting the structural elements in a poem can sometimes lead to interesting discoveries about how that poem works. In this case, though, all it has me doing is questioning the effectiveness of the rhymes in stanza three ("wither" and "whither" are pronounced the same, which doesn't seem like Frost as his best).
Of course, the content is at least as important as the form. Read the poem a couple of times, look for patterns, develops ideas of your own about what the poem means, and test those ideas in a rereading of the poem. To me, the first stanza reads more like an allegory than a nature poem; the speaker gives few details about the world he moves through. This stanza, to me, says pretty much (using metaphors) that the speaker has lived away from home for a good while, experienced much, and then returned home. The adventure of life (or maybe something else) is over.
The winter imagery through the rest of the poem reinforces this sense of an ending, even as it may hint that another beginning is just around the corner. The poem ends with a question about how well humans tend to or should accept "the end / Of a love or a season." They shouldn't accept it gracefully and meekly, the speaker seems to think.
In the poem 'Reluctance' by Robert Frost the poet sets out to describe walks he has enjoyed in the Fall,just as winter is coming on, and the thoughts they engendered in his mind about beginnings and endings and our response to them as humans. Firstly, after taking us with him on some of these virtual walks, he describes how falling Fall leaves behave, before he goes on to tackle us.'Out, over, climbed,looked,descended,come are all from the language of 'place' and help to give a sense of distance to us and to the poem, creating vistas for us as if Frost is talking about the whole world. The tone is reflective, even slightly melancholy as the poet contemplates the end of summer walks. He seems reluctant to end one phase of summer and enter another - winter. The oak too is reluctant, does not want to give up its leaves. He then moves on to us, and to how we handle change - with graceful acceptance or reluctant refusal.
To me, the point of this poem, the thesis that Frost is trying to set out, is that human beings are dead if they have no ambition. If we yield gracefully (as he says in the last stanza) when things end (whether a season or a love), we commit treason against ourselves.
I think that Frost does a very nice job of illustrating his point. What makes this most effective, to me is how he abruptly changes the tone and the message of the poem in the last two lines of the third stanza. Up to then, the poem seems mournful -- like he has accepted (except perhaps for the oak leaves) the end of the season and the end of the journey.
But in those last eight lines, Frost turns the whole poem around and says "No!" In those lines he says that the heart still wants to wander and learn and that we must never stop trying to do so.