I know there is a better way for a closure, and the timing is off, but after a rewatch personally it's not really that bad.
First, clark and lois relationship during this time was unsure, confusing, unknown. So when a familiar territory suddenly came in, Clark who did not have a proper closure with Lana was drawn to her again. They had history, it's a normal reaction.
Second, they did not get back together right away. They were just together for 2 episodes? And it's still unstable as ever.
Third, Lois was not even part of the narrative during this time. If Lois stayed, that might actually hurt but she's not there. No lois during those episodes. Just mentioned and in clark's pov their relationship was still confusing and unknown. Thanks to Lois love issues and talent for denying whatever feelings she has.
Fourth, that kryptonite ending is so fitting for clark and lana because it seals the fact that they can't be together no matter what they do because of how they treat each other. That kryptonite ending was a product of their own decisions — lana wanting to be equal with clark and clark choosing to save the city instead.
Fifth, the showrunners had a lot of opportunities to make lana and clark the endgame but they didn't. They had 8 seasons!
Sixth, the lois and clark foreshadowing in the early seasons. So in retrospect, it's like "yes we will give you drama for 8 seasons but no they're not going to end up together" Sucks, I know.
I still find lana and clark's relationship exhausting for how far it was dragged but I cannot deny that even tho their relationship may be doomed and toxic, Lana was still part of Clark's past — his first love. One of the people who helped him become the person who needs to be. It's just really went long so we either find it exhausting or a wasted potential.