The first time you used 'MTOM' I thought you meant MTOW. Now I'm not sure what you mean by it.
Mass is the correct term to use for aircraft, not weight. Mass is constant, weight depends on gravitational force.
That is relative. It won't be a 5th gen fighter until it has the indigenous or equivalent turbofan engine producing 35k lbf wet thrust and provides enough dry thrust to make it supercruise. Until then, it is regarded as a 4.5 gen fighter.
The whole generation thing is a useless marketing term, don't get yourself hung up in them. The F-35 is supposedly 5th generation but is barely supersonic even with afterburner.
The list of reasons why you want more power to weight is long. For example, more power means lifting more weapons and fuel, from higher runways, in warmer weather, to greater altitudes. It means more room to grow with future upgrades. It means you can do all of that with more reliability in case of a single engine failure. Then of course all the obvious air combat stuff.
Is it that crucial?
Somewhat underpowered 2030s LO fighter aircraft is still a 2030s LO fighter aircraft. It won't be the first somewhat underpowered aircraft in history.
Sure, not great, but not terrible either.
I suppose not, and other aircraft have tried and failed to gain traction for similar reasons. But IMO it would seem kind of pointless to knowingly design an aircraft to be worse than necessary, which is why I also don't think it is as heavy as some suggest. This is a solidly medium-weight fighter. The engine selection backs that up.
