Also I lost to a meh player's mediocre snake after I 3 stocked his main, rip MU exp I never knew ye
fucking karma for having mean thoughts about snake the night before after playing Messi (of colorado) and realizing that character is bullshit
please rework dair to not be a multhit dair that can be started instantly out of a SH and yet end right as you land for a perfect follow-up from a quick OoS option; and remove hurtbox from grenade/make hurtbox invincible so hitting it doesn't give snake a get out of jail free card from so many punishes, kill moves and shield pressure
please, he would be so much less bullshit
People who are unfamiliar with Snake's mechanics because they haven't played a decent Snake before are almost always at a loss for why they blow up so much. You don't have to insult Babaganoush for your own MU inexperience.
Now about Dair and Grenades: a frame-perfect Dair OoS takes 8 frames to begin (5 frames of jumpsquat + 3-frame startup) and has very poor horizontal reach. While it does end in a highly rewarding meteor, you have to hit a frame-unsafe move decently far into Snake's shield to get hit by it. Furthermore, its 4 hits allow for a lot of SDI - try to move away from Snake if he's stomping in place, or through him if he's coming towards you with the Dair. Snake's aerial mobility is nothing to write home about, so once he starts a SH Dair his landing options are pretty limited. It is perfectly feasible to SDI in such a way that the meteor doesn't connect, though it is quite difficult for big-bodied characters like DK and Bowser.
Snake can fastfall to hit with only 3 hits of the Dair, which combos into several things. Ftilt, Utilt and sticky are all fairly guaranteed, and in theory so is grab but in practice the timing is tricky (since you have to time the Dair to land right as the 3rd hitbox comes out to get maximum frame advantage) so try buffering a spotdodge and you might escape. Also if you manage to shield at any point before the Dair finishes it is quite shield-grabbable.
Grenades are Snake's most versatile tool. For those unaware, Snake can pull a grenade and shield to drop it, then pick it up like a normal item by wavedashing OoS. Landing with a grenade pulled also has next to no landing lag, so it's common for Snake players to recover high and pull a grenade (often B-reversing to mixup the landing) to land lagglessly if they don't get hit or trade of they do. Shield-dropping a grenade (not to be confused with shield dropping through a platform) is also a potent way to discourage attackers, since they run the risk of hitting the grenade while Snake blocks it and proceeds to combo off of the explosion, which sends people upwards.
There are three main counterplay options against a Snake who is in shield with a grenade sitting at his feet.
1. Grab him. Grab beats shield (surprise, surprise) without detonating the grenade. From here you can try to time your throw so that the explosion happens during the 7-frame invincibility period of all throws (very hard) or choose a quick throw so that you can shield/roll/jump/etc before the grenade blows up. This may be difficult or impossible depending on how long the grenade has been cooked and how fast your character's fastest throw is. Also Snake is heavy, so throw animations take longer than usual.
2. Space a move on his shield or use a projectile. When Snake shield drops a grenade, it lands ever so slightly behind him and on the ground. In the air, he holds the grenade behind his body. You can hit Snake('s shield) without hitting the grenade hurtbox and juggle/put pressure on him that way. Obviously this is easier for characters with good disjointed attacks like Marth and Ivysaur, which is one of the reasons Snake tends to struggle against such characters. Projectiles also serve a similar function of safely dealing with shield + grenade.
3. Wait. Snake has just pulled an explosive that is guaranteed to go off in two seconds or less. If he wants to just stand there blocking, let him deplete his own shield. If he rolls, he has either moved toward you with lag or given up stage positioning. If he jumps, he has put himself at a disadvantage. The smarter Snakes will glide toss (which has laughable distance on it, btw) or wavedash OoS to pick up the grenade and then throw it or shield/spotdodge. Regardless of which option they choose, the grenade will always detonate at the same time, and as the timer goes down, the probability of Snake picking one of those options goes up.
Notice that grenades are most defensively potent when the opponent is not grabbing, spacing particularly well, or being patient. Force Snake to be more creative by selecting the appropriate counterplay (this will depend on player and character matchup) or punish him for not adapting.
If you still want to change/rework either of these moves, we might have to get into a deeper discussion of Snake's design. Losing the potency of either puts a severe damper on his punish game and leaves him fewer ways to transition away from his poor neutral.
TL;DR Space around Dair, SDI if you get hit. Beat defensive grenades by grabbing, spacing, projectiles, or waiting Snake out.