I think that the whole dilemma started with making UT2003 out of the original Unreal Championship.
It was too different in movement, weapon-strength and visual feel. A few liked UT2003 better and a lot liked the original UT better. So we got a split fanbase. And this time not between mutators or gametypes but two different games.
Then UT2004 came along fixing (or at least going in the right direction with) some things like weapon strength, and visual feel. Still it was UT2003 with tweaks when you look at the gametypes that had been in UT2003.
Additionally it introduced ONS and reintroduced Assault. The former had a huge impact, although it wasn't perfect because of map design and some mechanics.
So we now had a playerbase split between mainly UT2004 and UT (and a few for UT2003) which are still completely different.
Now UT3 was released. It had again a completely different visual feel, neither being close to UT nor UT2k3 or 2k4. The movement was also different from UT, although closer to it than UT2kx. So we have still people saying UT3 doesn't feel like UT. THe UT2k4-lovers love the 2k4 movement and the others love either the UT3- or the UT- movement.
Another mistake, IMHO, was the complete change of ONS into Warfare instead of improving what the ONS community wanted and putting it into an ONS2.0. WAR should have been an addititional gametype as it was first described in Conquest.
This complete change split the former UT2k4 ONS-fanbase with some preferring WAR while others still preferred ONS.
So, since Ut2k3 we got split, split, split, split...
A franchise that allows so many different playstyles even within one iteration MUST NOT IN ANY CASE change the basic game-mechanics too much in the vanilla version compared to the previous version, because the changes already will take place within one iteration itself via mutators etc... ...improvements are necessary, additions are welcome, but changes in basically every aspect of the game is an absolute NO.
Unfortunately the past cannot be undone. The only chance I see to revive a multiplayer-franchise with the name Unreal in it would be a few years of not releasing anything and then making a new Unreal MP title which is not named Tournament.