OK, we have a very large "old-school" site. HTML 1, 2. No CSS, no fancy-schmancy formatting. It extensively used legitimate image "tricks" long ago to create effects ahead of it's time (IT's creation time). They still work entirely well on most browsers. But, there are, for instance, 1x1 pixel blank or colored dot "images" which are resized in the IMG tag to width=100 x height=1 in order to space things like tables which could not otherwise reliably be done back then on all browsers. An old trick some on here may recall. There was originally no ulterior motive as far as SEO, just neat site design. So most ALT tags were non-existent or "" since there was no need for them.
Well, nowadays ALT on "images" is apparently required, and supposedly is important to search engines. So (until everything can be rewritten) what would be the best ALT to put on these IMGs? apparently "" (our preference, since it simply ignored the effect if they had images turned off) is no longer acceptable. If we put "widget site" or some variation on each instance on the page I understand G will detect and frown upon that (besides the fact that it looks like @#$% when someone has images turned off)? If we put ALT="spacer" or "white blank" will we be SE optimized for that instead of the main topic? How about " ", or "-" or "|" (although this could totally screw up the appearance for ACTUAL users)? Yet another instance of NEEDING to design for SE's rather than users.
It seems the search engines have no consideration for older sites which pre-date themselves and were designed in complete innocence of SEO. Not everyone who "writes for their visitors," and has done so for a long time, can keep up with the whims of ALL the search engines and browsers when they constantly change their preferences. They USED to respect "HTML 2.0" just as we respect original '57 Corvettes. We literally spend more time rewriting these days than writing new content.