It is not a bad formation; more like it is was being used (and maybe still used) as if it was the pinnacle of all formations. In fact, these days, it is stronger as compared to way before because attacking midfielders seems to be doing the job of strikers. This season, I noticed that formations that have little in the middle in terms of MCs have been doing well. First in my league used mostly a formation with 1 MC and another formation with no MC (only 1 loss and 2 draws for this team in the league so far), and in another league, 1st is using that same formation with the 1 MC. In the Cup, my team was knocked-out by a team that used 1 MC for his away match and no MC for his home match. It looks like some things have changed in the game.
For me, for how it was before (2015) in this game, 4-5-1(V) lacked punch in attack. And if you did not have good enough AML and AMRs, things could be worst. For my main team (the first team), I had a lot of problems getting AMLs and AMRs on the server my account was. Others like Nik were getting wingers on their servers, and that too fast trainers and even with special ability, while me, I could hardly find even a decent one despite checking the transfer market nearly every morning every day. I got a 'second-hand' DML/ML/AML in the 2nd season, and in both 2nd and 3rd seasons, I had to use the scouts' list: 2nd season got an AMR/AMC/AML and 3rd season got an MR/AMR. I created a test account, (which is now the account I am using), and despite this account being on a different server, still there were deficiencies in terms of nordgen wingers. I would not blame all the failures that occurred during the period I was using 4-5-1(V) on the formation itself. Some failures were due to my lack of knowledge of the game itself. It is just that it has not worked for me as compared to the likes of Nik. But, the main difference is that my team was like 5 stars, with 5-6 stars wingers while others who had success a lot with that formation had 6 star teams with wingers at 7-stars and sometimes even more. So, this contributed too.
This game, especially during a period, seemed to favour narrow formations like narrow diamond, 4-3N-1-2 and 4-1-3N-2. Formations like narrow diamond were as equally strong in defence (and maybe even better) compared to 4-5-1(V), but had more presence in attack, and later with the coming of the new version with 3D on all supported platforms, certain styles seemed to be more pleasurable to watch as shown by the highlights and also appeared to be like really dominating the opponent as compared to 4-5-1V which was like boring. With further changes (assistant manager and effect of bonuses), formations like 4-5-1V and the usual style used with it, that is defensive and counter-attacks, were no more that good. The game favoured intense styles and formations. High pressing and high defensive lines (like Barcelona was playing at a time) became the successful ones. Even 4-3N-2W-1 was not that good (maybe talisman can comment about that). Much much later, which comes to this season, it seems that game is favouring some styles again. In other words, it is like the game has been changing so as to reflect how things have changed in football in real life, that is different formations and styles being dominant and successful at different periods.
All that being said, I will still use 4-5-1(V), but only where I feel it is appropriate to use.