You have one daily until level 5. Getting +3 to hit with that daily > +1 to hit with that daily. In other encounters, you have 1 or 2 encounter powers, again giving you very few options to add the +3 to. Having the most important powers be even more accurate can at least be comparable to having all your powers more accurate. This depends on whether you want higher damage output on average per round, or want to hit with your daily/encounter power.
Dwarven Weapon Training
Eladrin Soldier
For eladrin soldier, you gain access to the greatspear, giving you reach without losing proficiency bonus compared to your longsword, and a damage increase. With d8 becoming d10 and +2 to your damage, it is going to likely increase the damage per round compared to a simple +1 to hit. This depends on the accuracy you already have. The dwarf is in a similar position, gaining damage from both the fixed +2, and the higher damage dice of superior weaponry.
TWF is already inferior to weapon focus, and is either (a) an addition to weapon focus or (b) a prerequisite to two weapon defense. The latter is often the main reason to take TWF ... the damage boost is secondary.
All of the above feats give a conditional bonus to hit and/or (usually 'or') damage. All are mechanically inferior to Weapon Expertise, even before 15th level. That's a pretty large selection of feats marginalized by a single feat in the PHB 2.
To use your statement above, the opportunity cost of taking any of the feats I listed is too high, when the alternative is a flat +1 to hit in all situations with your primary weapon.
(a) You get more than one feat option so the option of "this is better than that" is only relevant at the earliest levels. At best the list is "if you liked these feats, you'll be interested in expertise".
(b) Some, not all, but some, have benefits that weapon expertise cannot offer (such as heavy thrown, reach or defensive properties of the superior weapons; the ability to get two weapon defense).
(c) Some of them are not mechanically inferior to Weapon Expertise. Action Surge, for example, gives a greater bonus than Weapon Expertise until level 25. If the goal is "hit with daily powers" then it does that job better. More so, the extra damage from the racial weapon specializations will arguably give more damage per round than a slight increase in accuracy.
(d) There already exists feat that overlap each other and some feats that are purely better than others (in some situations). For example a multiclass feat gives a skill AND an additional power. Two Weapon Fighting gives a +1 to only one of the weapons, compared to weapon focus, etc.
There are going to be feats that will likely be best to pick first amongst it's peers. Few of the feats are obsoleted by the expertise feats ... most would just get pushed back a bit as they work well
with expertise. It's not replacing so much as delaying. Now, for people that wouldn't be taking those feats in the first place, it's harder to argue that expertise is the correct choice.