### Godot version

v4.2.beta1.official [b1371806a]

### System information

Ubuntu 22.04.3 LTS 22.04 - X11 - GLES3 (Compatibility) - AMD Radeon RX 560 Series (polaris11, LLVM 15.0.7, DRM 3.42, 5.15.0-88-generic) () - AMD Ryzen 3 1200 Quad-Core Processor (4 Threads)

### Issue description

![image](https://github.com/godotengine/godot/assets/1330325/7a986599-5a68-42a4-beb1-5d3b4bf7db6b)
![image](https://github.com/godotengine/godot/assets/1330325/e8b8546b-b47b-4add-9567-7f70709ab03c)

Culling 3D goes bellow 60 fps even with just about 50 simple animated models. With v4.2.dev6.official [57a6813bb] many more models can be spawned without fps drop. However, both versions do show high cpu usage for culling 3D. Without animations there's barely any usage.

### Steps to reproduce

Spawn models with animation with the Compatibility renderer.

### Minimal reproduction project

[CullMRP.zip](https://github.com/godotengine/godot/files/13400514/CullMRP.zip)

global_shader_uniforms.variables.clear();
}
GLuint MaterialStorage::global_shader_parameters_get_uniform_buffer() const {
	return global_shader_uniforms.buffer;
}
int32_t MaterialStorage::global_shader_parameters_instance_allocate(RID p_instance) {
	ERR_FAIL_COND_V(global_shader_uniforms.instance_buffer_pos.has(p_instance), -1);
	int32_t pos = _global_shader_uniform_allocate(ShaderLanguage::MAX_INSTANCE_UNIFORM_INDICES);
	global_shader_uniforms.instance_buffer_pos[p_instance] = pos; 
	ERR_FAIL_COND_V_MSG(pos < 0, -1, "Too many instances using shader instance variables. Increase buffer size in Project Settings.");
	global_shader_uniforms.buffer_usage[pos].elements = ShaderLanguage::MAX_INSTANCE_UNIFORM_INDICES;
	return pos;
}
void MaterialStorage::global_shader_parameters_instance_free(RID p_instance) {
	ERR_FAIL_COND(!global_shader_uniforms.instance_buffer_pos.has(p_instance));
	int32_t pos = global_shader_uniforms.instance_buffer_pos[p_instance];
	if (pos >= 0) {
		global_shader_uniforms.buffer_usage[pos].elements = 0;
	}
	global_shader_uniforms.instance_buffer_pos.erase(p_instance);
}
void MaterialStorage::global_shader_parameters_instance_update(RID p_instance, int p_index, const Variant &p_value, int p_flags_count) {