In Wordsworth’s “Tintern Abbey,” what changes in the speaker's attitude toward nature do lines 88-93 specifically describe?

In this poem in general, the speaker is detailing the ways in which he has been affected by nature throughout his life, and particularly the ways in which the natural landscape around Tintern Abbey has sustained him while he has been away from it. Prior to these lines, he has described the "rapture" stimulated in him by nature when he was a boy, suggesting that children are most in tune with nature. In these lines, then, he is expressing the recognition that it is not necessarily a loss for the speaker to lose that kind of connection with nature, almost animalistic as it was. Indeed, now an adult with a different relationship to nature, he does not "mourn nor murmur" the loss of this relationship, because a new one is now being forged which seems adequate "recompense" to him.
As an adult, indeed, he is able to view nature in a way that is deeper than the "thoughtless" approach of the young man who is only viscerally affected by it, almost without thinking. Now, the speaker allows nature to stimulate in him feelings about "humanity," its power able to "chasten and subdue" him rather than simply stoke a rapture within him. The "sublime" which he now feels in nature is more of a contemplative one, an understanding that everything on earth, both human and belonging to the landscape, is actually "interfused" because of the existence of the natural world around us. As such, the emotions which the speaker can be driven to by exposure to nature are now deeper, more pensive, and more considered.

In these lines, the speaker describes his growing awareness that there is more than just simple beauty in the scenes of nature by which he has been so affected. He realizes that there is something deeper, something bigger running through these scenes, as well as "in the mind of man." The speaker describes a spirit that directs the thoughts of everything with the power to think and exists in all things. He seems to describe a kind of life force, something that connects all things in nature and all people to one another. This is an incredibly romantic idea. This awareness of the sublime linking everything is the result of the speaker's more mature reflections on nature brought about by his experiences with humanity, since he saw the natural scenes he describes some five years ago.