Yes, they’re not interchangeable.

"je trouve ça" is followed by an adjective, and can be translated by "I find it …" rather than by "I think that …".

Je trouve ça beau = I think it’s beautiful

Je trouve ça bizarre qu’il soit parti aussi vite = I find it weird that he left so quickly

"je trouve que" is followed by a clause. that is often omitted in English.

Je trouve que tu devrais faire plus d’efforts = I think you should make more efforts

Je trouve que ça te va bien = I think it looks good on you

Note that you can "transform" sentences with je trouve ça to use je trouve que by adding c’est before the adjective, making it a clause.

Je trouve ça bizarre

Je trouve que c’est bizarre