What clear holes do they have? Obviously if Kane gets hurt they're in trouble but the same could be said for Lukaku, Salah, Aubameyang, Morata or even Aguero. Any team that loses their top scorer will be in trouble. United I don't think improved they remained the same, Chelsea lost a very good keeper which could be an issue and only really added Kovacic who we don't know how well he'll do in the premier league, Arsenal added the most to help their squad but they were way off so don't think it bridges the gap.
Where do you see Dembele, Alderweireld or Rose are disgruntled? Known of them stopped training to force a move or mare any frustrations known. Dembele turned down Inter I heard so he didn't want to go that bad. United have more unsettled players it would seem.
Offensively they hopefully have Lamela all year who's a threat, Moura looks good in preseason, Alli could go back to a couple years ago when he was scoring more. Even Llorente could be more useful this season which will help. If Winks is healthy he's a top DM, Wanyama has moments of being a good one, Dier has a lot to be desired but gets the job done and Dembele is coming off a strong WC. That midfield is on par with most of the top 6.
Who should they have brought in? Ajax may sell De Ligt in January if out of the Champions league, he would be a good buy but I don't think Ajax was selling this early. Grealish would just be depth but they kept Onomah and Nkoudou so far who could provide similar. Again I don't see who in the starting 11 that they should've replaced? Dembele is the only questionable one but they have depth in that spot so unless they unloaded Dembele first it made no sense to add another one.
Its not just if Kane goes down it is that they need him (and Eriksen) to play every game in the PL and CL because the back-up options are terrible. Plus Arsenal- Lacazette, Chelsea- Giroud and especially City- Jesus all have viable back-up options.
United added Fred which isn't much but they were ahead of us last year and that is more than we did, I don't see any reason to question how Kovacic will do in the Prem he is a great player, Arsenal is still behind us even with the additions.
As for the starting 11 I think we needed to improve the DM spot, I do not see Winks as a top DM at all and Dembele clearly took a step back last year. As well they need to upgrade the Son/Lamela spot as well. Both are much better in limited roles or against lesser teams. They are ok as starters but I think the point is to improve and that is what a transfer could have done. As mentioned bringing in depth behind Kane and Eriksen was desperately needed as we are way too reliant on both.
As for who I would have brought in:
In a perfect, non pie in the sky (Bale/Modric) but still unlikely scenario: Martial, Kovacic, De Ligt, Grealish
In a more realistic and guys we were linked to: Grealish, Cook, De Ligt and a young striker
Others probably have a better sense of names that were available but I can't imagine it was that hard for Tottenham to find guys who could improve their club considering every club out there in every other transfer window were able to.
Alderweireld has complained about his role last year and it is doubtful it is increased that much this year or at best he is going to be in a rotation. Dembele said he wanted a new contract that has not been offered and Rose has made very public comments about leaving at the start of the season.