More like we already have a big rebuild and issue with ego/attitude/professionalism on our hands at the moment. Dembele maybe a worthy gamble to add quality to a certain area of the team, but I am not sure about being one of the core player going through this rebuild. You know like how at sometimes in recent past, there is no denying about RashFord, Martial and Greenwood potential. But giving the key to the team when they're still too young mentally, then the gain shortlived, leaving us with even bigger rebuild that it supposed to be.
Dembele is already 25 years old. I wouldn't classify that as being too young to be a key player. And no, even if Dembele came he would not receive that kind of special treatment. Why do you think that?
Dembele has turned things around at Barcelona, AFTER Xavi and Barca stated he would have no place in their plans. That does not scream as an ego/professionalism issue from Dembele. If anything, that is willpower to turn his Barca days (And in the grand scheme of things, his whole career) around.
At 25 years old, Dembele should be entering his prime soon. He just needs his next club to have competent medical staffs and fitness coaches. Robben was the same injury-prone type of player at Chelsea and Real Madrid, but he turned things around at Bayern Munich and played well into his 30s. Coincidentally, Robben joined Bayern at the same age as Dembele currently is right now: 25 years old. See the pattern here?
If his injuries come back those teams have something to fall back on. Transfers are a gamble and he is a big gamble.
It's because we are in a very unideal condition as a football team that we NEED to take risks now. The failed transfers of previous years left us in frustration not only because of reasons but also because of how lazy they were scouting-wise. We mostly opted for the "safe" Premier League options (Harry Maguire, Wan-bissaka...) or big stars who everyone knew would cost a ton of money (Di Maria, Pogba...). We rarely ventured ourselves into unknown territories and got the type of "great risk great reward" transfers. Bruno Fernandes was one of the rare times when we went ahead with our scouting judgement and not what Europe thought as "trendy". That's why Bruno's transfer generated so much excitement when he flourished and took us to top 4 two times.
Why are we looking at Liverpool with envy these days? It's not just because they are quite successful these days. It's because we see how they dare to take risk with assertion and actual cleverness. They took risk on Klopp although he failed badly at Dortmund's last season. They took risk on Mane (Premier League's midtable player according the CAF at that time). They took risk on Robertson despite he was a Championship player with Hull (while we only got to Maguire AFTER he had made a name for himself at Leicester). They took risk on Salah despite he was labelled as a Chelsea reject who couldn't make it in the Premier League. The list just goes on. They took on many gambles while they were still rebuilding, not concerning if they could afford to take them at that time (Like how many of us are perceiving the Dembele deal right now). That assertiveness is what drives Liverpool's success at the moment.
You mentioned Dembele as a big gamble. That is correct. Big gambles come with big rewards. We are in very weakened state right now as a team. I don't think we can't afford big gambles because we are currently bad. It's exactly because we are bad that we need to be brave and take on big gambles, trusting our own assessment of the situation rather than how the mass perceives it. Dembele comes with great risk, but that's exactly why we have a chance to secure a player of his calibre (When he is in top form) right now for free.
A lot of us share the same sentiment that we need to reinforce too many positions this summer. Isn't a free, effective transfer of a top-class player in our supposedly weak position the exact thing we need? If we are still afraid of the risk and not dare to action, dare I ask which transfer is exactly a sure-fire bet in this day and age anyway?