Rey's actions are justified and he has a right to be more careful with his feelings.
1) There is a difference in loving someone and being in love with someone. Kria was his first love and he will always love her but he has had to deal with 2 heart breaks ever since then and he will be more careful about his feelings. So he has a right to not reciprocate Kria's feelings.
2) For the past 2 years, Rey has believed Kria used him, and she left him with no answers. Now he knows the truth but he still needs time to analyze everything and deal with his emotions before he moves ahead.
3) And its just a kiss!!! They were drunk, and it was an emotional time, and both the characters vented their thoughts and clarified the misunderstandings, so the kiss was bound to happen. For the past years, when both misunderstood each other, and all that pent up feelings that they could not explain or voice it, when everything was finally out in the open, the kiss was the perfect way of ending the scene.
4) Also, Rey doesn't know if Kria will stay in St. Louis or go back to NY. Let her earn his confidence first and then love is bound to happen. Why would Rey fall in love with her and go through all the trouble just to find her leaving again. So he has to be extra careful with his feelings. He has had a history of failing relationships, so he needs to be careful. "Fool me once, shame on you, Fool me twice, shame on me"
( As a viewer, I am worried after every good scenes between Kria and Rey, thinking Shakti may leave again. To be honest, she is the most successful person in the D3 gang. She has a busy schedule, what if she leaves again? I had watched D3 and I was equally heartbroken to see Rey cry and those last few episodes was brutal for all of us, and then with a new entrant it was horrible. So I keep telling myself to be less involved and be less attached to D3, but I love these two characters.)
5) Lastly, with Rey unsure about his feelings, it gives us one more opportunity to watch them fall in love again. All the wooing scenes, the excitement of new love, new feelings, ALL OVER AGAIN, what else could we ask for? I am glad that the CVs aren't assuming that a kiss would lead to "happily ever after" , let them work hard and earn that love. I am excited to watch the upcoming episodes.
(But I am hoping the new entrant does not play a havoc in Rey and Kria's lives. Since the CVs confirmed there is no love triangle in Swaron's lives, what if she was meant for Kriayansh. But anyway that is least of my worries right now. For the time being, I am HAPPY as Rey knows why Kria left, and everything is cleared, and I am waiting to see them fall in love again. Whether its real or reel life, falling in love/ wooing is the best phase of love.