Downside risks / why I sold / convince me I'm wrong

I bought Appen at $3.30 in 2016. I've been selling a few parcels in the mid 20s to deploy into other smaller tech stocks, however today I sold a large parcel as I'm losing conviction in the company. There's a few things that have been bothering me about Appen. Feel free to convince me I'm wrong.

1. The CEO of Figure Eight didn't stick around, and he seems to have launched a competing company.

2. I'm skeptical about how relevant Appen's 1 million global crowd will be to the way AI is done in the future. I can't believe that humans will be training machines like this forever. It's a bit low-tech for my liking.

3. The valuation is high, which wouldn't bother me if the two points above didn't. But when even punters on hotcopper reckon a stock is overvalued like I've been seeing here lately, I reevaluate.

4. The two recent acquisitions themselves are quite large, and I have a gut feeling a writedown is coming.

5. Lumpy revenue bothers me. Whilst this is a WAAAX stock, it's not even worthy of being compared to Wisetech, Altium or Xero, who have revenue visibility years into the future. I know the recent acquisition is meant to move Appen to a SAAS model, but why do they need to acquire a company to do that?

6.CEO is not the founder. How much does he really care?

Yes, much of this criticism comes from Roger Montgomery, but he has a point in my opinion.

Appen is still one of my biggest holdings, so I hope I'm wrong about all this. But I'm thinking of selling out completely.