I mean, there have been several explanations as to how it might not really be a plot hole. The main one being that humans and likely even Time Lords have all the cells in their bodies replaced by new cells after so many years (I think it's about 7 years) and that could be why Kazran could touch his younger self. This is also ed by the fact that every time we see the Doctor (or anyone else for that matter) meet a younger or older version of themselves, they're always years and even decades apart. Granted, it's possible that the writers didn't consider this when writing the episode, and IF that's the case, then it's still not a great look that they need the fans to bend over backwards to find the logic to plug up the plot holes

In your response to Melody, I think you partially explained the difference between Kazran and Rose's respective situations. Rose initially summoned the Reapers by saving her father and strengthened them enough to get into the church by creating a small paradox when she touches her younger self. However, that didn't initiate the Blinovitch Limitations Effect because of the cellular regeneration theory (since they were about 20 years apart). While the Doctor explains that running into, or touching your younger self can cause a paradox, I don't think that it's a big enough paradox to have any major or lasting effects in most cases because we've seen the Doctor, as well as others, do it several times before (though the Doctor tries not making a habit out of it in case one of those meetings does lead to drastic consequences) and when it happens, the different versions are usually years or even decades apart, thus they would've already replaced their cells. Granted, that COULD just be because the Doctor is a Time Lord, but since we see it happen with Kazran, I don't think being a Time Lord really matters all that much in those instances (aside from Time Lords having a sort of resistance to paradoxes). Rose simply tampered with the already weakened timeline for a second time, which was enough to strengthen the Reapers, which is how they were able to appear inside the old church to feed off the timeline, but her and her younger self didn't explode because of their age difference and cellular replacement. So had the Reapers not already been there from her first interference with time by saving her dad, I don't think anything significant (if anything at all) would've happened from her holding herself.

P.S. Sorry for my comment being so long. It's just kinda weird for me to explain and I hope it makes sense lol.

While that's possible, it could also be because we as humans replace all the cells in our bodies after so many years. So, having such a large age gap, old Kazran's cells would've been replaced several times over since the time he was the young Kazran.

Daehock's explanation is exactly what I was also thinking while reading the article lol.

As for Dani-Kessel-Odom's comment regarding Rose Tyler and the Reapers; I think the reason why the Reapers were "summoned" to the inside of the church is because she had already tampered with time (specifically a fixed point) by saving her father, which made her a direct link to the Reapers even being there in the first place. And touching herself as a baby just tampered with time again enough for the Reapers to by the Doctor's explanation that they would have a harder time feeding on older things at first. That could explain how the Reapers were able to appear without initiating the Blinovitch Limitation Effect (because of the explanation that Daehock gave).