This page should be rewritten so that it can be understood by the average person reading a printed copy. Betza notation and interactive diagrams are fine as supplements to the content, but they should not replace an English-language description of how each piece moves. This goes for every page using Betza notation and interactive diagrams.

This is debatable. For games with excessively large numbers of piece types, English-language descriptions get extremely tedious to read. Especially if the pieces are so asymmetric as typical Shogi pieces. Good examples as to which this will lead are the Wikipedia pages on the large Shogi variants. People that think such a representation is useful can print the Wikipedia page. We can put links to these in the articles; it makes little sense to duplicate them.

IMO English text is a very poor method to convey the move information; it is an extremely verbose way to give very little and very simple information. A compact, easy to understand abbreviation will be highly superior. Betza description offers such an abbreviation, and the Shogi pieces only use the most elementary elements of it (forward, backward, vertical, sideway, R, B, F, W). This should hardly be beyond the grasp of an "average person"; readers can in general be assumed to be familiar with the concept of 'abbreviation'. If the issue is that F and W are too cryptic, a single line of text could be added to explain that these are just a 'one-step Bishop and Rook'.

In addition, the piece graphics in the image itself already encodes the moves; no textual description for individual pieces is really necessary. If you think the graphics is not entirely self-evident, the logical solution would be to include an explanation of how the graphics should be interpreted. Like:

The images used for the pieces in the diagram indicates how they move. Stepping pieces are represented by squares, with a 'bite' take out of them in directions where they cannot move. Longer-range sliding moves protrude out of these squares, and will be marked by a radial line if they have unlimited range. Absence of such a marking implies a range of maximally two steps in the corresponding direction.

I don't think it would be optimal to repeat this in every article that uses these graphics, though. A better solution would then be to write a separate article on the mnemonic piece set, and put a link to that in all the articles using them.

I can add that apart from the graphical encoding, and the description through the trivial subset of Betza notation, each of which should already have been entirely sufficient, the interactive diagram also contains a complete set of move diagrams of all the pieces, as a standard feature.