To understand Hinduism properly, first you should have some knowledge about Sanskrit Language or Veda Bhasha. Sanskrit is language of Attributes. It doesn't have proper nouns. Krishna is named for person who is "black". Shiva is named for a person who is "auspicious". But a person has many attributes. You can call a person by any of his attributes. But Lord or Parabrahma has infinite attributes. So, Parabrahma has infinte names. Unlike other languages, a Sanskrit name gives some info or qualities a person possess. So, if you come across a name "Shiva" in scripture, you should understand that person has aan attribute "auspiciousness" besides other additional attributes.
My intention is not to boast Sanskrit language, but to affirm that Sanskrit language is eternal and so the language of Vedas (Veda Bhasha). Sanskrit has no need to evolve in vocabulary like other languages, though there may be changes in grammar.
Vedas are eternal scriptures and they are valid for all times. It doesn't matter which yuga you live or which epoch (Kalpa) you live or in which Loka you dwell. Vedas are infallible truthtruths where each and everything can be verifiable. This is what Sri Swami Prabhavanada says in the book Spiritual heritage of India,
The Rishis who have gone into deep Tapsya heard them (in transcendental consciousness) . We may not understand them properly and verify all their contents by our limited consciousness. Thus, we need to study them under a knowledgeable Guru (preceptor).
Now coming to your question, you main question is about idol worship. No scripture explicitly rejectedrejects idol worship, including Vedas. Indeed, they are not just idols. They have prana in them. We invite Lord or Consciousness into them with Mantras. This process is called Prana Pratishta. Those who condemn idol worship are just half baked Jivas. However, we don't need to invite Lord into Swayambhu (self manifested) murtis, such as Tirupati Venkateswara and Jyotirlingas of Shiva.
Refer introduction section of the above linked pagethis page to know summary of first 8 verses. This verse says both Meditation and karma are important. Indeed, verses 9 to 18 give emphasis for both Karma and Upāsanā.
Griffith also uses the words Sambhuti"Sambhuti" and Asambhuti"Asambhuti" in his translation. So, Sambhuti and Asambhuti are manifested and unmanifested and this verse says one must worship both states of Supreme Brahman.
The translation in your question says it is bad to "worship natural things". But on the other hand, we see divinity in everything. This divinity can be explained with simple logic as said by Swami Krishnananda in his book "lessons on upanishads". I don't quote it here as this will make answer very lengthy.
Verse 32.3 from Vajasaneyi Samhita of Shukla Yajurveda with traslationtranslation of Griffith
This verse says about formlessdescribes formless and unmanifested aspect. As we know, Brahman is manifested and unmanifested and at the same time He has form and He is formless.
Krishna Paramatma never explicitly rejected idol worship in Bhagavad Gita. I think translations you come across were given by some Hindu haters or by haters of idol worship (to uphold their own faithReligion).
Lord says the following in Bhagavdgita 7.20. (translated by A Mahadeva Sastri),
Adishankara commentary says (translated A Mahadeva Sastri)
Brihadaranyaka Upanishad 2.3.1 (translated by Swami Madhavananda) says
Adishankara says (translated by Swami Madhavananda)
This is what Lord says in 7.24 (translated by A Mahadeva Sastry),
Sri Adishankaracharya explains this verses as follows (translated by A Mahadeva Sastry)
Here Krishna never condemns any worship of Saguna form or idol worship. He just says that fools and ignorant people do not know his higher nature which is immutable and unsurpassed. Here Krishna says about His highest nature but this doesn't mean that Lord won't descend by donning Physical body. Lord has both manifested and unmanifested form. He says only few persons know His true form by going into transcendental consciousness. Lord says His true nature at highest level was unborn and imperishable. ThisThis is what Adishankaracharya says,
So, finally to know proper meaning of Hindu Scriptures either read them in Sanskrit (Veda Bhasha) or in any language with commentaries of knowledgable Acharya or learn them under a knowledgable Guru.