Too much going on with the Arjuns. Quite a few new concepts/versions are being invested upon at the same time. The Arjun Mk1 has deficiencies like the Tejas Mk1. But unlike the Tejas the Arjun has no fixed upgradation path. The IA is afraid that investing too much on one version (Arjun Mk1A) could cause them to lose out on the other upcoming versions(Like the GNMBT).
A few years back you could argue Arjun's upgradation path was more certain & I would've agree with you. The aerospace ecosystem has leaped ahead considerably in the last few years, largely due to IAF's backing. IA has done none of that unfortunately. The relation between the parent service endorsement & growth of industry is profound, this needs to be a subject of serious study.
That doesn't mean all problems are gone. Look at shipbuilding, still plenty of problems with delays & cost overruns. But the industry is strong & stable. That's where I see the aerospace ecosystem going in some time.