This basically means that you just need one arbitrary code execution vulnerability in Firefox and it's game over. In contrast, if you have the same in Chrome, Edge, or Safari, then it's just the first step - you now have an environment where you can run arbitrary exploit code, but you can't make (most) system calls and you have to find another exploit to escape from the sandbox. Typical Chrome compromises are the result of chaining half a dozen vulnerabilities together.
but it was fully backwards compatible with GW-Basic
No it wasn't. I had to install GWBASIC separately from a DOS 4 install disk after upgrading to DOS 5, because the Chain Reaction GWBASIC game didn't work with QBASIC.
Robots don't feel those emotions, and have committed no massacres on that scale. I trust robots more than I trust humans.
Do you trust a gun? Do you trust a bomb? Of course not, because the concept is meaningless: neither will cause harm without instructions from a human. Both can magnify the amount of harm that a human can do. Autonomous weapons, of which landmines are the simplest possible case, expand both the quantity that a person can do harm and the time over which they can do it.
During the cold war, there were at least two incidents where humans refused to follow legitimate orders to launch nuclear weapons - in either case, the likely outcome of following the orders would have been the deaths of many millions. The worst atrocities of the second world war were caused by people 'just following orders'. And you think that it's a good idea to remove the part of the chain of command capable of disobeying orders.
It's about both cost and risk analysis. If you've got a lot of infrastructure, then you've probably already got a team of decent admins. Adding another server has a very small marginal cost. If you haven't, then the cost is basically the cost of hiring a sysadmin. Even the cheapest full-time sysadmin costs a lot more than you can easily spend with GitHub. Alternatively, you get one of your devs to run it. Now you have a service that is only understood well by one person, where installing security updates (let alone testing them first) is nowhere near that top priority in that person's professional life, and where at even one hour a week spent on sysadmin tasks you're still spending a lot more than an equivalent service from GitHub would cost.
In both of the latter cases, the competition for GitHub isn't a competent and motivated in-house team. It is almost certainly better to run your own infrastructure well, but the competition for GitHub is running your own infrastructure badly and they're a very attractive proposition in that comparison.
Outsourcing things that are not your core competency is not intrinsically bad, the problem is when people outsource things that are their core competency (e.g. software companies deciding to outsource all of the development - it's not a huge step from there to the people working for the outsourcing company to decide to also handle outsourcing management and start up a competitor, with all of the expertise that should be yours), or outsourcing without doing a proper cost-benefit analysis (other than 'oh, look, it's cheaper this quarter!').
If you think outsourcing storage of documents is bad remember that, legal companies, hospitals and so on have been doing this for decades without issues - storing large quantities of paper / microfiche is not their core competency and there are companies that can, due to economies of scale, do it much cheaper. Oh, and if that still scares you, remember that most companies outsource storing all of their money as well...
"It says he made us all to be just like him. So if we're dumb, then god is dumb, and maybe even a little ugly on the side." -- Frank Zappa