SRK had been in the industry for little over a year when Baazigar and Darr released, so I wont call them a turning point.
But a lead hero cannot play anti-heroes his entire life, so DDLJ is SRK's turning point. He said no to the movie many times as he wanted to be an action hero, and that same year he even had action movies KA, Trimurti and Ram Jaane. But the public made their choice and wanted to see SRK as a romantic hero. Basically Baazigar and Darr had this fantasy lover boy who was crazy for the lead heroine, and that was the part that the audience (especially females) liked and gave their sympathy to, but those movies also had him as a murderous psychopath, which meant that he couldn't be a huge star on the back of those roles. DDLJ gave the audience the fantasy aspect while removing the anti-hero part, and there was no looking back.
After DDLJ SRK became known as the king of romance and his biggest hits are form that genre, or from movies where he is playing a romantic hero regardless of the genre (like in K3G where the movie is a Family Drama but in the first half the focus is on SRK-Kajol romance).