I have this question that I thought was well-suited to a site that describes itself as:
...a question and answer site for professionals, academics, and students working within the systems development life cycle.
When I graduated from college, the phrase "software engineering" had not yet entered academic vernacular and I graduated as an electrical engineer, so I hope you can understand my confusion as to why I thought mine was a sensible question to ask.
Please note that I don't feel bad that it's going to be closed as off-topic. All SE sites need to manage their scope or things get out of hand. However, it seemed obvious (even after revewing your on/off topics page) to ask about how to judge when to exclude browser version support when developing an app on a site that claims to be about the system development life cycle.
After reviewing your various FAQ pages further, it appears this site is principally focused on the internals (how do I plan for my software's end-of-life?) and wants to avoid the externals (how do I protect mystelf from another software package's end-of-life?). Cool.
I ask that you to consider a comment left by @DocBrown and an additional insight from myself for addition to your on/off-topic page. If only to help the old fat guys like me who still haunt the halls of software development. Doc Brown said:
...concerning your "life cycle argument": you are playing with words, the specific life cycle of one specific software product of one specific vendor is definitely not on-topic here.
Therefore, please consider adding to your FAQ page:
Questions about the life cycle of specific products are off-topic.
Questions relating the the business of using software including (but not limited to) the financial impact of supporting software, when to decide to end support, and how to plan for the end-of-life of dependent applications are off-topic.
Thanks for your patience.