You started listing things as if literally everything about DMC2 was a failure. And yet the only things I would consider are true problems are one boss that can't defend itself when you get close to it and occasional fight that needs to be done with guns.Or maybe your attempt at defending it.
Seriously now, I don't know your criteria, but as for me, a game with an incredibly dull story, an even duller protagonist, poor gameplay with practically every enemy being cheesable with maxed out pistols and tedious level design, with all that running around in overly big areas, I tend to judge that pretty much a failure, yeah. You may disagree but in my eyes, there are FAR too many problems to say it's even decent.
Besides, I didn't even say it's a failure in every aspect. I do recognize the - IMO, very few - good things that are there, I've said it in some posts in the past.
Maybe I sound like with someone with too high expectations (as if that wasn't legit after a game as good as Devil May Cry back in the day anyway), but you sound like someone in denial to me. It is no secret that DMC2's development process was a VERY messed up one and the game turned out badly as a result, by the developers' own admission too. That's why I said it needs a remake the most.
The story is dull? Well yeah, but only seems that way cause of dark atmosphere and silent Dante, it has as much content as any other DMC game save for DMC4 maybe, the only thing that's really different is that you don't have Dante and the bosses doing some intro talk to cover it up.
Gameplay is improvement compared to DMC1, save for sword moves. Trickster style was actually based on some of Dante's evasive moves in DMC2. I actually love the button layout, it's friendly to those who don't live and breathe video games.
Level design might be a little poor, it's very open yet didn't use it in proper amount, but is in no way more tedious than running up and down the tower, or up and down the castle, or back and forth through that mixture of settings on Fortuna island.
You can beat all the enemies with maxed out guns, but who says you HAVE to do it? In fact, I find slashing through a group to be a better option.
If you say something is bad often enough, everyone starts to believe it, even developers. You think Itsuno would be so embarrassed of it if DMC2 wasn't treated with nothing but disdain from the moment the first details came out?
Yes, it needs a remake, but not because it's a failure. It just needs to improve on good ideas it had and to finally get rid of the stigma.