Normally yes, but I mean, Cloud displays more maturity than a 16 year old, so I don't think the mental age gap is really that big, despite the technicality of it. He is running a business and at the start of CoT he's the one encouraging Tifa that everything will be ok, that he'll be there to remind her of how strong she is, so it's not like he doesn't try to be supportive emotionally. It's only when he falls into his own bout of depression does this encouragement dissappear, but then again the depression is largely gone by the end of Advent Children.
Might I also add, that at the start of CoT, Cloud is very much trying his best to be supportive, and Tifa herself acknowledges that he is trying for her despite his glaring personal issues:
I'd also like to add that Denzel looked up to Cloud specifically. Tifa also thinks he resembles a young dad, so there's that aswell. He couldn't have been that terrible of a father figure.
Hell, even as a child he displays some emotional maturity/development beyond that of the other boys his age:
1. Even though Cloud knew the truth about what happened on the mountain, he chose to take the blame for it because he thought it would bring Tifa shame if he told the truth. He did this as an 8(?) year old boy. The other boys immediately lied to cover their own hides, and never owned up to it, at that.
Not to mention the bravery needed to follow her up the mountain, something the other boys also lacked.
2. Not seeing Tifa as a trophy to be won. Atleast one of the other boys sent Tifa a letter that implied he owned her.
tl;dr: Cloud doesn't get it right all the time when it comes to their relationship, but he tries, and it's not plausible for a relationship to be flawless, so I don't know where the idea that Cloud is necessarily an 'undesirable' partner for Tifa comes from, weird technical mental age gap or not.