IE is an old and outdated design and not as secure as a modern browser built from the ground up. IE isn’t as secure, isn’t as fast, and is harder to customize with new features. It is an old legacy product.
Think about that 80 year old bridge the replaced along a highway near your town. It still worked but was too narrow for modern traffic and had been patched a million times. That is how IE is right now.
Some websites INTENTIONALLY do not work with IE because of the security concerns and I think this is a good idea. Why allow exposure of personal and private data when safe alternatives exist? Many medical and banking websites no longer worth with IE.
I had one just the other day. The people needed to transmit medical data and IE was no longer working. The computer was the equivalent of that 80 year old bridge so get replaced even though it still worked and could have been upgraded. It would have cost as much or more than the complete replacement and still not been as good. The hardware and software had been patched and band-aided by others so many times that the thing was a mess. It was far easier and less disruptive to just get rid of the outdated system and replace it with something modern.
I was just reading an article about how 2019 has been a record year for data breaches. I only expect it to get worse before it gets better, especially with around 25% of all computers still being on Windows 7 and losing support in a few short weeks. A lot of banks and internet service providers plan to block access from Windows 7 computers and I see this as a good thing. The local university blocked this as of today and others around the country have done this or plan to do the same. Some will drop support on the last day of Win 7 support (Jan 14th) while others plan to give users an extra month or two. UC-Berkeley gives a absolute deadline of March 1st before they are blocked. You can find notices like this on bank and university sites around the country. https://security.berkeley.edu/news/microsoft-windows-7-end-life
It doesn’t make sense for companies to continue to support and upgrade multiple lines of browsers and operating systems. I think the Windows 10 upgrade cycle is a good idea. MS directly copied Apple with OSX on this one and I think it is a good idea to try and standardize things on a common platform.