How come supports don't get mobility?

In the current state of things, it feels like a lot of supports do not even have enough safely to perform their jobs, given that they don't have mobility. A lot of them can't be too far away if they want to make good use of many of their abilities. So they have to constantly put themselves in danger. Enemy assassins can likely just one-shot them if they ever get within like 500 units radius of them. Not only that, if they are attempting to help a teammate in trouble, and their teammate is a noob and just dies really easily, the support likely gets killed to, just by even trying to help, since the enemies can probably can get around faster. This could happen even last season but not it seems like it's much easier to just instadie in these kind of situations where there's too little to try to do. That's right, if your teammates just dive the enemy backline, or even just position badly enough, you can be zoned out of even trying to help out at all in fights. And this can be true even if you build a defensive item against them. They just do so much damage now that the assassins will just one-shot you anyways.

On top of this, it's also just too unforgiving. One time where you just barely happened to get caught since the enemy jungler went down to bot and flash ulted you where you almost couldn't possibly survive, and then you're stuck being even more irrelevant the rest of the game. Once you're behind in levels, there's really not enough way to come back into the match anymore. If you stay in a lane, you still just get a fraction of the experience of its minions. And if you roam and get kills, you still only get a fraction of the kill xp since you only got an assist, and even if you got a kill, it was with assists and you still didn't get that much xp. That's right, even if you play really well and get a bunch of kills for your team, you still do not really bring yourself into much relevancy in fights. You'll probably just instadie to an enemy assassin as soon as you try to do anything, since unless you're really high elo your tanks will not know how to actually protect the backline. So yes, this doesn't make squishy supports bad, it just makes them really suck to play as in low or mid elo and I feel it really needs a change in this regard in order to make it more appealing to play as.

So, what are some ways to fix this problem? Well, there are tons of ways. The easiest way would be to bring the inspiration mastery back, so that low xp champions could actually have a more reasonable way of at least partially coming back. Alternatively, there could be some good new items in the shop that could be better at dealing with this, possibly even just one that gives the old inspiration ability. It could even just be tacked on to those nearly useless eye items, and then there'd be no worry about mids abusing them since it doesn't work unless you're behind in xp. Or, they could reduce the damage done by the keystone masteries as they seem to be a big part of what has thrown this season out of whack and why too many champions are snowballing too hard too easily. Or, as mentioned at the start, they could be given mobility, so that they could actually make more big plays themselves without just being in such dangerous of areas that they just instadie. There are many more possibilities, but these are what come to mind and there should be something here that can fix the problem.