1. If the reasoning is that a hostile foreign government could use sensitive data against the US and thus shouldn't be allowed to collect such data then such policy is being arbitrarily enforced. There are other companies (FaceApp comes to mind) that collect data on Americans that don't have such scrutiny from the executive branch. Furthermore, American companies that collect sensitive data regularly give access to foreign entities (e.g. Cambridge Analytica, which abused Facebook's sharing agreement with academic institutions but there nonetheless exists such sharing agreements). If the use of CIFIUS is a part of a broader strategy against China then such a strategy should be outlined somewhere, announced and debated in Congress. This is a special decision taken unilaterally against TikTok.
2. I don't think the executive branch's reasoning is limited to the potential of abuse. Representatives of the Trump administration have stated that they are concerned with data that TikTok currently collects, which they say merits a national security concern. It seems like they are making these claims to get the public on board with the measures, but claims like this require specifics and evidence. Even if I agree with TikTok being banned from the US over security concerns, I don't want to feel propagandized by the US government.
3. What sensitive data are we talking about!? This is the elephant in the room. It seems like the big concern is over email address + geographical location + TikTok viewing history + images of faces. TikTok still lives on platforms that are heavily sandboxed and secured by very interested teams at Google and Apple. Nobody has made a credible accusation that TikTok is exploiting some zero day to gain access to users' sensitive data.
4. This isn't a part of a broader talk about the dangers of tech companies collecting too much data. There doesn't seem to be any plans to restrict data collection nation-wide. Maybe the executive branch is taking this on a case-by-case basis but a more reasonable explanation seems to be that Trump simply doesn't like TikTok or is using his power to muscle out foreign businesses as a bargaining chip in a larger China dispute.