You could repot this snake plant into a container one size larger (at this size, pots tend to increase width in 2" increments). A ceramic or terra cotta pot, being heavier than this plastic pot, will help balance the top-heavy nature of these plants. The lean could be due to inadequate light; while tolerant of low-light conditions, snake plants thrive if given moderate levels of light. Set back from a bright southern or western window or closer to a northern or eastern window would help it to flop less. Giving plants that tend to get light from one main direction (as is common with houseplants using window light) a quarter-rotation every week or so will help balance-out future growth to avoid leaning.

Repotting plants in soil this old will also help freshen-up the root zone for better plant health overall. Remove what old soil you can and replace it with new potting soil. (Given that snake plants do best when kept drier than most houseplants, it's best to avoid soils advertising "moisture control" or better moisture retention, as these can easily stay too wet.) Make sure the plant stays at the same depth when repotted; you don't want it buried deeper in the new pot, so you may need to put a few handfuls of soil into the new pot first (as larger pots are also slightly deeper). Having the topmost soil be about an inch or two beneath the rim of the pot is ideal to allow room for water to soak into the soil without spilling soil over the edge. If old roots have rotted away over the years due to soil that has compressed over time, this insufficient anchoring in the soil could also help explain the tipsy nature of the leaves. Using new soil and only watering the plant when it becomes quite dry should promote healthy roots. (Water it well when it needs it, just infrequently enough that it has a chance to dry out. Always empty the saucer of drained water afterwards.)

Miri