There is nothing wrong with feeding your eclectus pellets, so long as you give them the right ones.
I give mine Paradise Pellets by VetaFarm. This is a specially designed recipe specifically for frugivores (Fruit eaters). Eclectus are frugivores.
These pellets were created by Taronga Zoo for their Toucans and is specifically low in iron which is ideal for eclectus.
If a ZOO is OK with feeding their own eclectus these pellets, I am OK with it. Vets recommend pellets! Pellets are the easiest way to give your parrot a complete diet, which can be very difficult when giving only fruit and veg. My eclectus is a picky eater so it is literally IMPOSSIBLE to give him a balanced diet any other way, and it's awful having so many 'experts' online making other people feel bad and stressing about giving their bird pellets when it is right and it is working for them. Maybe there will be instances where pellet diet didn't work for a particular individual.. That doesn't mean it won't work for your bird, nor does it make it bad. Some people have bad reactions to eating a peanut! Are peanuts bad now because a group of people got on the internet saying they had personal experience that removing peanuts from their diet made them healthier? Remember that for every person on the internet saying pellets are awful and their birds improved SO MUCH when they removed pellets, there are the opposite people saying their birds are doing just fine on pellets and even improved SO MUCH when they switched to a pellet diet.
An incomplete fresh diet is WORSE then a complete pellet diet designed for these animals.
Don't get sucked into the hysteria. People with no veterinary or scientific knowledge giving advice to people based on anecdotal opinions that have never been proven. Trust the scientists and vets, not random people on the internet

Remember that 'breeders' are not scientists or vets either.
Go to your vet. Get some blood work done. Find out if he is getting the appropriate vitamins and minerals and put your mind at ease and adjust if necessary, instead of relying on people who know nothing at all about your birds health.
There are different pellets designed for different birds: Get the right one and you will be fine.
Remember, pellets are a complete diet. Issues with eclectus come about from either vitamin deficiency, or getting too much of some vitamins. If you give your parrots pellets that have x% of vitamin Y, then give your parrot heaps of veg and fruit that also has loads of vitamin Y... They can now be overloaded with vitamin Y. So be mindful of that as well. Pellets come with a guideline of how much to feed vs fresh fruit and veg for a reason. If you change this, you may not be giving your parrot a balanced diet any more.
If you choose to do a complete fresh diet, that's fine too. If done properly, this would be the most ideal diet for them. But it is risky and you must make sure it is a balanced diet and they are getting ALL of the vitamins and minerals they need. If you can do that, do it! It would be a wonderful diet.