World Travel Awards defines itself as the leading authority that recognizes and rewards excellence in the Tourism and Travel industry. It is hard to categorize it as legit or a scam, because based on how the awards are organized, we may come to divergent conclusions. 
In some of the most respected awards such as the Oscars, you are not required to pay any fee for nomination. This is not the case with World Travel Awards. It is as though the awards do not seek to recognize the best agencies rather the agencies that are able to pay them at least £650. The world Travel awards nominations list is always short. This is not because they have shortlisted nominees but it is simply because those were the people who were willing to pay them £399 or £499 plus £299 for advertising.
In other words, World Travel Awards has presented itself as a brand that endorses Travel brands through receiving payments that accounted for as though they are nomination fees. If you are looking for the best agency in a given country, World Travel Awards would not be the place to find that company. This does not imply that they endorse fake companies rather they do not present you with all the best agencies a given destination has to offer.
Imagine if you had a competition such as the UEFA champions league but instead of featuring the top European teams such as Real Madrid, Barcelona, Manchester City, Liverpool among other top teams, you instead feature teams in the Tercera Division, English Football League One, Serie C among other lowers divisions teams whose participation is on a non-merit based participation. This is exactly how World Travel Awards works; you are not guaranteed to find the best agencies rather mere agencies in the given category. Sometimes they feature reputable companies and other times; it is a total disappointment.
In conclusion, we cannot say World Travel Awards is a scam but even though it is not a scam, it should never be considered as a directory for the best companies in the whole world through their nomination list.