TAA only looks worse than no AA if you have a super high res image with next to no sub-pixel detail… or a very small screen where you are getting some blending from human eyeballs not being perfectly sharp in the first place.

I don’t know that the line is going to be on things like grainy low-sample path tracing. For one thing you don’t use TAA for that, you need specific denoising (ray reconstruction is sometimes bundled with DLSS, but it’s technically its own thing and DLSS is often used independently from it). The buildup of GI over time isn’t TAA, it’s temporal accumulation, where you add rays from multiple frames over time to flesh out the sample.

I can accept as a matter of personal preference to say you prefer an oversharpened, crinkly image over a more natural, softer image, so I can accept a preference for all the missed edges and fine detail of edge detection-based blur AA, but there’s no reason decent TAA would look blurry and in any case that’s exactly the part where modern upscaling used as AA has an edge because there’s definitely no washed out details when using DLSS when compared to no AA or SMAA at the same native res. You often get additional generated detail and less blur than native with those.