Try firing a safe ranged weapon- nerf, water, whatever- into a group of your friends doing some sparring. Odds are good that unless you're trained somehow, you're going to hit someone you didn't intend to.
3E had a lame "if you roll in the cover bonus range, but still roll high enough to hit the AC of the covering creature" (which almost never happened, hence the reason it was lame) rule and 3.5 did not have an "accidentally hit someone else" missile rule, so I don't actually see how 4E is worse in that regard.
Missile fire may be fast, but your windows of opportunity are small.
I suspect that the windows of opportunity that you are talking about are much larger than you claim in real melee.
Real melee is not like a Jackie Chan movie where people are constantly flying all over the place lightning quick. Real melee is small groups of people sparring where their eyes are on their target and although they sometimes switch positions and such quickly (especially in a flurry of blows), there is a LOT of time (seconds at a time) where they are close to stationary, sizing up their opponent, shifting on their feet, looking for an opening.
Watch a boxing match or any martial arts match.
And if we are talking a fantasy Jackie Chan where everyone is zipping around the battlefield combat, then not having a firing into melee rule is preferable because the entire combat is cinematic and not realistic. Firing into melee rules are unneccesary (and can even be considered counter to the desired effect, YMMV) in a cinematic feel combat concept.
Actually, some of us revel in the firing into melee rules. You can feel the tension when someone who isn't skilled at it is forced by circumstances to attempt it...and it really rocks if he pulls it off despite the odds. Drama and tension!
Its also cool when someone attempts a shot nobody else could do without rolling a Nat 20...because he knows he can do it.
I want my snipers to be snipers.
In 4E, sniper = proficient.
There are very few bonus/penalty to hit feats and attack modifiers (9 in the PHB) in 4E. And, the attack modifiers from 3.5 have for the most part, been cut in half. The reason is that limiting the number and potency of these also limits the broken synergies that plagued 3E/3.5. Adding to damage is less unbalancing than adding to "to hit" because to hit changes probabilities.
There are many powers that give a bonus or penalty to hit, but they tend to only last a round.
This was a good design decision. Only keeping the most important of these and halving most of the kept ones is a good thing, both because it limits the number of rules that are needed to be known and because it minimizes the chances of the D20 roll becoming a mere formality in the multi-to hit synergy situations. Firing in Melee is pretty much a minor attack penalty, precisely because all 3E snipers took the feat and 3E non-snipers rarely fired into melee.
I don't see a lot of drama and tension in a -4 to hit rule. The 3.5 "snipers" had the feat, so it did not apply to them and other PCs rarely attempted such a suboptimal option. At most, it is a rare amount of drama and tension. YMMV.
But if it bugs you, add a house rule (I would suggest no more than -2 in the 4E model). I did back in 3E. For most of our 3E/3.5 game years we ran with a "aim carefully at -4 per the book" and "aim carelessly, no penalty, but one could accidentally hit an ally" rules because a "-4 to hit" rule had no drama or tension.
It was a blast for the entire table (usually including the player of the PC that got hit) when a PC got shot by another, regardless of people on the message boards saying how that would "totally suck". It was rare enough that it added to the fun, but often enough to add tension in some circumstances. And it gave an option to the players who did not have the feat to still have a decent chance to hit, but at a risk.
It's much more drama and tension to risk an ally than it is to hit a hard to hit enemy. The -4 rule was just plain lame.
This rule also allowed for one to miss an enemy and hit a different enemy by accident (e.g. the first enemy ducks and the second takes it in the face). It felt great (and cinematic) for players to suddenly have a miss turn into a hit after all.
That is, of course, the opinion to which you are fully entitled. Personally, I'd much rather have rules about firing into melee than worry about "marked" and "bloodied."
Sounds like you prefer 3.5.