For TIFF (and most formats) that's heavily dependent on if you're talking about implementing a reader or a writer for the format. TIFF readers need to handle JPEG streams, so in that sense implementing a general purpose TIFF reader is a superset of implementing a general purpose JPEG reader.
On the other hand, TIFF writers can (very conveniently!) be almost as simple as you want, including no compression at all, just blobs of raw pixel values, and a smattering of tags for width, height, pixel format, and that's it. The only thing simpler to output IMO would be uncompressed ASCII formats like XPM.
So in that sense you're correct- the simplest possible JPEG writer is much more complicated than the simplest possible TIFF writer, but TIFF in general is extensible to a fault (arguably), in the sense that the number of possible combinations of pixel and metadata encodings you have to prepare yourself for when opening arbitrary .tif files are far greater than when opening arbitrary .jpg files, including JPEGs within TIFFs.
Back in the days TIF was just a large uncompressed file.
The initial format is older than GIF87a (no animation which people associate GIF nowadays with). It had header but that pretty much it. Of course the format developed with time and even added LZW once the patent expired. Currently TIF is all kind of things, so writing a fully feature reader is a proper challenge (perhaps not coding-wise, but understand it and implementing the myriads of types/extensions, etc.)
On the other hand, TIFF writers can (very conveniently!) be almost as simple as you want, including no compression at all, just blobs of raw pixel values, and a smattering of tags for width, height, pixel format, and that's it. The only thing simpler to output IMO would be uncompressed ASCII formats like XPM.
So in that sense you're correct- the simplest possible JPEG writer is much more complicated than the simplest possible TIFF writer, but TIFF in general is extensible to a fault (arguably), in the sense that the number of possible combinations of pixel and metadata encodings you have to prepare yourself for when opening arbitrary .tif files are far greater than when opening arbitrary .jpg files, including JPEGs within TIFFs.